You are given two strings a and b consisting of lowercase English letters, both of length n. The characters of both strings have indices from 1 to n, inclusive. 

You are allowed to do the following changes: 

  * Choose any index i (1 ≤ i ≤ n) and swap characters a_i and b_i; 
  * Choose any index i (1 ≤ i ≤ n) and swap characters a_i and a_{n - i + 1}; 
  * Choose any index i (1 ≤ i ≤ n) and swap characters b_i and b_{n - i + 1}. 



Note that if n is odd, you are formally allowed to swap a_{⌈n/2⌉} with a_{⌈n/2⌉} (and the same with the string b) but this move is useless. Also you can swap two equal characters but this operation is useless as well.

You have to make these strings equal by applying any number of changes described above, in any order. But it is obvious that it may be impossible to make two strings equal by these swaps.

In one preprocess move you can replace a character in a with another character. In other words, in a single preprocess move you can choose any index i (1 ≤ i ≤ n), any character c and set a_i := c.

Your task is to find the minimum number of preprocess moves to apply in such a way that after them you can make strings a and b equal by applying some number of changes described in the list above.

Note that the number of changes you make after the preprocess moves does not matter. Also note that you cannot apply preprocess moves to the string b or make any preprocess moves after the first change is made.

Input

The first line of the input contains one integer n (1 ≤ n ≤ 10^5) — the length of strings a and b.

The second line contains the string a consisting of exactly n lowercase English letters.

The third line contains the string b consisting of exactly n lowercase English letters.

Output

Print a single integer — the minimum number of preprocess moves to apply before changes, so that it is possible to make the string a equal to string b with a sequence of changes from the list above.

Examples

Input

7
abacaba
bacabaa


Output

4


Input

5
zcabd
dbacz


Output

0

Note

In the first example preprocess moves are as follows: a_1 := 'b', a_3 := 'c', a_4 := 'a' and a_5:='b'. Afterwards, a = "bbcabba". Then we can obtain equal strings by the following sequence of changes: swap(a_2, b_2) and swap(a_2, a_6). There is no way to use fewer than 4 preprocess moves before a sequence of changes to make string equal, so the answer in this example is 4.

In the second example no preprocess moves are required. We can use the following sequence of changes to make a and b equal: swap(b_1, b_5), swap(a_2, a_4).
import javax.print.attribute.standard.PrinterMessageFromOperator;
import java.io.*;
import java.math.BigDecimal;
import java.math.BigInteger;
import java.util.*;
public class Main {
    public static void main(String[] args) throws Exception {
        new Main().run();}

//    int[] h,ne,to,wt;
//    int ct = 0;
//    int n;
//    void graph(int n,int m){
//        h = new int[n];
//        Arrays.fill(h,-1);
////        sccno = new int[n];
////        dfn = new int[n];
////        low = new int[n];
////        iscut = new boolean[n];
//        ne = new int[2*m];
//        to = new int[2*m];
//        wt = new int[2*m];
//        ct = 0;
//    }
//    void add(int u,int v,int w){
//        to[ct] = v;
//        ne[ct] = h[u];
//        wt[ct] = w;
//        h[u] = ct++;
//    }
//
//    int color[],dfn[],low[],stack[] = new int[1000000],cnt[];
//    int sccno[];
//    boolean iscut[];
//    int time = 0,top = 0;
//    int scc_cnt = 0;
//
//    // 有向图的强连通分量
//    void tarjan(int u) {
//        low[u] = dfn[u]= ++time;
//        stack[top++] = u;
//        for(int i=h[u];i!=-1;i=ne[i]) {
//            int v = to[i];
//            if(dfn[v]==0) {
//                tarjan(v);
//                low[u]=Math.min(low[u],low[v]);
//            } else if(sccno[v]==0) {
//                // dfn>0 but sccno==0, means it's in current stack
//                low[u]=Math.min(low[u],low[v]);
//            }
//        }
//
//        if(dfn[u]==low[u]) {
//            sccno[u] = ++scc_cnt;
//            while(stack[top-1]!=u) {
//                sccno[stack[top-1]] = scc_cnt;
//                --top;
//            }
//            --top;
//        }
//    }
//
//    //缩点, topology sort
//    int[] h1,to1,ne1;
//    int ct1 = 0;
//    void point(){
//        for(int i=0;i<n;i++) {
//            if(dfn[i]==0) tarjan(i);//有可能图不连通，所以要循环判断。
//        }
//        // 入度
//        int du[] = new int[scc_cnt+1];
//        h1 = new int[scc_cnt+1];
//        Arrays.fill(h1, -1);
//        to1 = new int[scc_cnt*scc_cnt];
//        ne1 = new int[scc_cnt*scc_cnt];
//        // scc_cnt 个点
//
//        for(int i=1;i<=n;i++) {
//            for(int j=h[i]; j!=-1; j=ne[j]) {
//                int y = to[j];
//                if(sccno[i] != sccno[y]) {
//                    // add(sccno[i],sccno[y]);  // 建新图
//                    to1[ct1] = sccno[y];
//                    ne1[ct1] = h[sccno[i]];
//                    h[sccno[i]] = ct1++;
//                    du[sccno[y]]++; //存入度
//                }
//            }
//        }
//
//        int q[] = new int[100000];
//        int end = 0;
//        int st = 0;
//        for(int i=1;i<=scc_cnt;++i){
//            if(du[i]==0){
//                q[end++] = i;
//            }
//        }
//
//        int dp[] = new int[scc_cnt+1];
//        while(st<end){
//            int cur = q[st++];
//            for(int i=h1[cur];i!=-1;i=ne1[i]){
//                int y = to[i];
//                // dp[y] += dp[cur];
//                if(--du[y]==0){
//                    q[end++] = y;
//                }
//            }
//        }
//    }
//
//
//
//
//    int fa[];
//    int faw[];
//
//    int dep = -1;
//    int pt = 0;
//    void go(int rt,int f,int dd){
//
//        int p = 0;
//        stk[p] = rt;
//        lk[p] = 0;
//        fk[p] = f;p++;
//        while(p>0) {
//            int cur = stk[p - 1];
//            int fp = fk[p - 1];
//            int ll = lk[p - 1];
//            p--;
//
//
//            if (ll > dep) {
//                dep = ll;
//                pt = cur;
//            }
//            for (int i = h[cur]; i != -1; i = ne[i]) {
//                int v = to[i];
//                if (fp == v) continue;
//
//                stk[p] = v;
//                lk[p] = ll + wt[i];
//                fk[p] = cur;
//                p++;
//            }
//        }
//    }
//    int pt1 = -1;
//    void go1(int rt,int f,int dd){
//
//        int p = 0;
//        stk[p] = rt;
//        lk[p] = 0;
//        fk[p] = f;p++;
//        while(p>0) {
//            int cur = stk[p - 1];
//            int fp = fk[p - 1];
//            int ll = lk[p - 1];
//            p--;
//
//
//            if (ll > dep) {
//                dep = ll;
//                pt1 = cur;
//            }
//
//            fa[cur] = fp;
//            for (int i = h[cur]; i != -1; i = ne[i]) {
//                int v = to[i];
//                if (v == fp) continue;
//                faw[v] = wt[i];
//                stk[p] = v;
//                lk[p] = ll + wt[i];
//                fk[p] = cur;
//                p++;
//            }
//        }
//    }
//
//    int r = 0;
//    int stk[] = new int[301];
//    int fk[] = new int[301];
//    int lk[] = new int[301];
//    void ddfs(int rt,int t1,int t2,int t3,int l){
//
//
//        int p = 0;
//        stk[p] = rt;
//        lk[p] = 0;
//        fk[p] = t3;p++;
//        while(p>0){
//            int cur = stk[p-1];
//            int fp = fk[p-1];
//            int ll = lk[p-1];
//            p--;
//            r = Math.max(r,ll);
//            for(int i=h[cur];i!=-1;i=ne[i]){
//                int v = to[i];
//                if(v==t1||v==t2||v==fp) continue;
//                stk[p] = v;
//                lk[p] = ll+wt[i];
//                fk[p] = cur;p++;
//            }
//        }
//
//
//
//    }


    static long mul(long a, long b, long p)
    {
        long res=0,base=a;
        while(b>0)
        {
            if((b&1L)>0)
                res=(res+base)%p;
            base=(base+base)%p;
            b>>=1;
        }
        return res;
    }

    static long mod_pow(long k,long n,long p){
        long res = 1L;
        long temp = k;
        while(n!=0L){
            if((n&1L)==1L){
                res = (res*temp)%p;
            }
            temp = (temp*temp)%p;
            n = n>>1L;
        }
        return res%p;
    }

    static int[] getNext(char[] cs){
        int len = cs.length;
        int next[] = new int[len+1];
        next[0] = -1;
        int j = -1;
        int i = 0;
        while(i<len){
            if(j==-1||cs[i]==cs[j]){
                next[++i] = ++j;
            }else{
                j = next[j];
            }
        }
        return next;
    }


    void solve() {



       int n  =ni();
       String a = ns();
       String b = ns();

       int add =0;
       for(int i=0,j=n-1;i<j;++i,--j){
           if(b.charAt(i)==b.charAt(j)){
               add += a.charAt(i)!=a.charAt(j)?1:0;
           }else{
                char c[] = {b.charAt(i), b.charAt(j)};
                char c1[] = {a.charAt(i),a.charAt(j)};

                int same = 0;
                if(c1[0]==c[0]||c1[0]==c[1]){
                    same++;
                }
               if(c1[1]==c[0]||c1[1]==c[1]){
                   same++;
               }
               if(c1[1]==c1[0]){
                   if(same==2){
                       add++;
                   }else{
                       add+=2;
                   }
               }else{
                   add += 2-same;
               }
           }
       }
       if(n%2==1&&a.charAt(n/2)!=b.charAt(n/2)){
           add++;
       }

       print(add);









        //N , M , K , a , b , c , d . 其中N , M是矩阵的行列数；K 是上锁的房间数目，(a, b)是起始位置，(c, d)是出口位置


//        int n = ni();
//        int m = ni();
//        int k = ni();
//        int a = ni();
//        int b = ni();
//        int c = ni();
//        int d = ni();
//
//
//        char cc[][] = nm(n,m);
//        char keys[][] = new char[n][m];
//
//        char ky = 'a';
//        for(int i=0;i<k;++i){
//            int x = ni();
//            int y = ni();
//            keys[x][y] = ky;
//            ky++;
//        }
//        int f1[] = {a,b,0};
//
//        int dd[][] = {{0,1},{0,-1},{1,0},{-1,0}};
//
//        Queue<int[]> q =  new LinkedList<>();
//        q.offer(f1);
//        int ts = 1;
//
//        boolean vis[][][] = new boolean[n][m][33];
//
//        while(q.size()>0){
//            int sz = q.size();
//            while(sz-->0) {
//                int cur[] = q.poll();
//                vis[cur[0]][cur[1]][cur[2]] = true;
//
//                int x = cur[0];
//                int y = cur[1];
//
//                for (int u[] : dd) {
//                       int lx = x +  u[0];
//                       int ly = y +  u[1];
//                       if (lx >= 0 && ly >= 0 && lx < n && ly < m && (cc[lx][ly] != '#')&&!vis[lx][ly][cur[2]]){
//                            char ck =cc[lx][ly];
//                            if(ck=='.'){
//                                if(lx==c&&ly==d){
//                                    println(ts); return;
//                                }
//                                if(keys[lx][ly]>='a'&&keys[lx][ly]<='z') {
//                                    int cao = cur[2] | (1 << (keys[lx][ly] - 'a'));
//                                    q.offer(new int[]{lx, ly, cao});
//                                    vis[lx][ly][cao] = true;
//                                }else {
//
//                                    q.offer(new int[]{lx, ly, cur[2]});
//                                }
//
//                            }else if(ck>='A'&&ck<='Z'){
//                                int g = 1<<(ck-'A');
//                                if((g&cur[2])>0){
//                                    if(lx==c&&ly==d){
//                                        println(ts); return;
//                                    }
//                                    if(keys[lx][ly]>='a'&&keys[lx][ly]<='z') {
//
//                                        int cao = cur[2] | (1 << (keys[lx][ly] - 'a'));
//                                        q.offer(new int[]{lx, ly, cao});
//                                        vis[lx][ly][cao] = true;;
//                                    }else {
//
//                                        q.offer(new int[]{lx, ly, cur[2]});
//                                    }
//                                }
//                            }
//                       }
//                }
//
//                }
//            ts++;
//        }
//        println(-1);




//        int n = ni();
//
//        HashSet<String> st = new HashSet<>();
//        HashMap<String,Integer> mp = new HashMap<>();
//
//
//        for(int i=0;i<n;++i){
//            String s  = ns();
//            int id= 1;
//            if(mp.containsKey(s)){
//                int u = mp.get(s);
//                id = u;
//
//            }
//
//            if(st.contains(s)) {
//
//                while (true) {
//                    String ts = s + id;
//                    if (!st.contains(ts)) {
//                        s = ts;
//                        break;
//                    }
//                    id++;
//                }
//                mp.put(s,id+1);
//            }else{
//                mp.put(s,1);
//            }
//            println(s);
//            st.add(s);
//
//        }

//        int t = ni();
//
//        for(int i=0;i<t;++i){
//            int n = ni();
//            long w[] = nal(n);
//
//            Map<Long,Long> mp = new HashMap<>();
//            PriorityQueue<long[]> q =new PriorityQueue<>((xx,xy)->{return Long.compare(xx[0],xy[0]);});
//
//            for(int j=0;j<n;++j){
//                q.offer(new long[]{w[j],0});
//                mp.put(w[j],mp.getOrDefault(w[j],0L)+1L);
//            }
//
//            while(q.size()>=2){
//                long f[] = q.poll();
//                long y1 = f[1];
//                if(y1==0){
//                    y1 = mp.get(f[0]);
//                    if(y1==1){
//                        mp.remove(f[0]);
//                    }else{
//                        mp.put(f[0],y1-1);
//                    }
//                }
//                long g[] = q.poll();
//                long y2 = g[1];
//                if(y2==0){
//                    y2 = mp.get(g[0]);
//                    if(y2==1){
//                        mp.remove(g[0]);
//                    }else{
//                        mp.put(g[0],y2-1);
//                    }
//                }
//                q.offer(new long[]{f[0]+g[0],2L*y1*y2});
//
//            }
//            long r[] = q.poll();
//            println(r[1]);
//
//
//
//
//        }
        //  int o= 9*8*7*6;
        //  println(o);


//       int t = ni();
//       for(int i=0;i<t;++i){
//           long a = nl();
//           int k  = ni();
//           if(k==1){
//               println(a);
//               continue;
//           }
//
//           int f = (int)(a%10L);
//           int s = 1;
//           int j = 0;
//           for(;j<30;j+=2){
//               int u = f-j;
//               if(u<0){
//                   u = 10+u;
//               }
//               s = u*s;
//               s = s%10;
//               if(s==k){
//                   break;
//               }
//           }
//
//           if(s==k) {
//               println(a - j - 2);
//           }else{
//               println(-1);
//           }
//
//
//
//
//       }

//     int m = ni();
//     h = new int[n];
//     to = new int[2*(n-1)];
//     ne = new int[2*(n-1)];
//     wt = new int[2*(n-1)];
//
//     for(int i=0;i<n-1;++i){
//         int u = ni()-1;
//         int v = ni()-1;
//
//     }
        //  long a[] = nal(n);


//        int n = ni();
//        int k = ni();
//        t1 = new long[200002];
//
//        int p[][] = new int[n][3];
//
//        for(int i=0;i<n;++i){
//            p[i][0]  = ni();
//            p[i][1]  = ni();
//            p[i][2]  = i+1;
//        }
//        Arrays.sort(p, new Comparator<int[]>() {
//            @Override
//            public int compare(int[] x, int[] y) {
//                if(x[1]!=y[1]){
//                    return Integer.compare(x[1],y[1]);
//                }
//                return Integer.compare(y[0], x[0]);
//            }
//        });
//
//        for(int i=0;i<n;++i){
//            int ck = p[i][0];
//
//        }

















    }









//    int []h,to,ne,wt;

    long t1[];
    //    long t2[];
    void update(long[] t,int i,long v){
        for(;i<t.length;i+=(i&-i)){
            t[i] += v;
        }
    }
    long get(long[] t,int i){
        long s = 0;
        for(;i>0;i-=(i&-i)){
            s += t[i];
        }
        return s;
    }

    int equal_bigger(long t[],long v){
        int s=0,p=0;
        for(int i=Integer.numberOfTrailingZeros(Integer.highestOneBit(t.length));i>=0;--i) {
            if(p+(1<<i)< t.length && s + t[p+(1<<i)] < v){
                v -= t[p+(1<<i)];
                p |= 1<<i;
            }
        }
        return p+1;
    }









    static class S{
        int l = 0;
        int r = 0 ;
        long le = 0;
        long ri = 0;
        long tot = 0;
        long all = 0;

        public S(int l,int r) {
            this.l = l;
            this.r = r;
        }
    }

    static S a[];
    static int[] o;

    static void init(int[] f){
        o = f;
        int len = o.length;
        a = new S[len*4];
        build(1,0,len-1);
    }

    static void build(int num,int l,int r){
        S cur = new S(l,r);
        if(l==r){
            a[num] = cur;
            return;
        }else{
            int m = (l+r)>>1;
            int le = num<<1;
            int ri = le|1;
            build(le, l,m);
            build(ri, m+1,r);
            a[num] = cur;
            pushup(num, le, ri);
        }
    }



    //    static int query(int num,int l,int r){
//
//        if(a[num].l>=l&&a[num].r<=r){
//            return a[num].tot;
//        }else{
//            int m = (a[num].l+a[num].r)>>1;
//            int le = num<<1;
//            int ri = le|1;
//            pushdown(num, le, ri);
//            int ma = 1;
//            int mi = 100000001;
//            if(l<=m) {
//                int r1 = query(le, l, r);
//                ma = ma*r1;
//
//            }
//            if(r>m){
//                int r2 = query(ri, l, r);
//                ma = ma*r2;
//            }
//            return ma;
//        }
//    }
    static long dd = 10007;
    static void update(int num,int l,long v){
        if(a[num].l==a[num].r){
            a[num].le = v%dd;
            a[num].ri = v%dd;
            a[num].all = v%dd;
            a[num].tot = v%dd;
        }else{
            int m = (a[num].l+a[num].r)>>1;
            int le = num<<1;
            int ri = le|1;
            pushdown(num, le, ri);
            if(l<=m){
                update(le,l,v);
            }
            if(l>m){
                update(ri,l,v);
            }
            pushup(num,le,ri);
        }
    }

    static void pushup(int num,int le,int ri){
        a[num].all = (a[le].all*a[ri].all)%dd;
        a[num].le = (a[le].le + a[le].all*a[ri].le)%dd;
        a[num].ri = (a[ri].ri + a[ri].all*a[le].ri)%dd;
        a[num].tot = (a[le].tot + a[ri].tot + a[le].ri*a[ri].le)%dd;


        //a[num].res[1] = Math.min(a[le].res[1],a[ri].res[1]);
    }
    static void pushdown(int num,int le,int ri){

    }


    int gcd(int a,int b){ return b==0?a: gcd(b,a%b);}
    InputStream is;PrintWriter out;
    void run() throws Exception {is = System.in;out = new PrintWriter(System.out);solve();out.flush();}
    private byte[] inbuf = new byte[2];
    public int lenbuf = 0, ptrbuf = 0;
    private int readByte() {
        if (lenbuf == -1) throw new InputMismatchException();
        if (ptrbuf >= lenbuf) {
            ptrbuf = 0;
            try {lenbuf = is.read(inbuf);} catch (IOException e) {throw new InputMismatchException();}
            if (lenbuf <= 0) return -1;
        }
        return inbuf[ptrbuf++];}
    private boolean isSpaceChar(int c) {return !(c >= 33 && c <= 126);}
    private int skip() {int b;while((b = readByte()) != -1 && isSpaceChar(b));return b;}
    private double nd() {return Double.parseDouble(ns());}
    private char nc() {return (char) skip();}
    private char ncc() {int b;while((b = readByte()) != -1 && !(b >= 32 && b <= 126));return (char)b;}
    private String ns() {int b = skip();StringBuilder sb = new StringBuilder();
        while (!(isSpaceChar(b))) { // when nextLine, (isSpaceChar(b) && b != ' ')
            sb.appendCodePoint(b);b = readByte(); }
        return sb.toString();}
    private char[] ns(int n) {char[] buf = new char[n];int b = skip(), p = 0;
        while (p < n && !(isSpaceChar(b))) { buf[p++] = (char) b;b = readByte(); }
        return n == p ? buf : Arrays.copyOf(buf, p);}
    private String nline() {int b = skip();StringBuilder sb = new StringBuilder();
        while (!isSpaceChar(b) || b == ' ') { sb.appendCodePoint(b);b = readByte(); }
        return sb.toString();}
    private char[][] nm(int n, int m) {char[][] a = new char[n][];for (int i = 0; i < n; i++) a[i] = ns(m);return a;}
    private int[] na(int n) {int[] a = new int[n];for (int i = 0; i < n; i++) a[i] = ni();return a;}
    private long[] nal(int n) { long[] a = new long[n];for (int i = 0; i < n; i++) a[i] = nl();return a;}
    private int ni() { int num = 0, b; boolean minus = false;
        while ((b = readByte()) != -1 && !((b >= '0' && b <= '9') || b == '-')){};
        if (b == '-') { minus = true; b = readByte(); }
        while (true) {
            if (b >= '0' && b <= '9') num = (num << 3) + (num << 1) + (b - '0');
            else return minus ? -num : num;
            b = readByte();}}
    private long nl() { long num = 0; int b;
        boolean minus = false;
        while ((b = readByte()) != -1 && !((b >= '0' && b <= '9') || b == '-')){};
        if (b == '-') { minus = true; b = readByte(); }
        while (true) {
            if (b >= '0' && b <= '9')  num = num * 10 + (b - '0');
            else return minus ? -num : num;
            b = readByte();}}
    void print(Object obj){out.print(obj);}
    void println(Object obj){out.println(obj);}
    void println(){out.println();}
}