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 java.io.*;
import java.util.*;
import java.lang.*;
import java.util.HashMap;
public class templ implements Runnable {
    class pair
    {
        int v,val;
        pair(int f,int s)
        {
            v=f;
            val=s;
        }
    }
    public static ArrayList<Integer> g[]=new ArrayList[1000000];
    public static int vis[]=new int[1000000];
    public static long M=1000000007;
    int binarySearch(int arr[], int l, int r, int x)
    {
        if (r >= l)
        {
            int mid = l + (r - l)/2;
            if (arr[mid] == x)
                return mid;
            if (arr[mid] > x)
                return binarySearch(arr, l, mid-1, x);
            return binarySearch(arr, mid+1, r, x);
        }
        return -1;
    }
    void merge1(int arr[], int l, int m, int r)
    {
        int n1 = m - l + 1;
        int n2 = r - m;
        int L[] = new int [n1];
        int R[] = new int [n2];
        for (int i=0; i<n1; ++i)
            L[i] = arr[l + i];
        for (int j=0; j<n2; ++j)
            R[j] = arr[m + 1+ j];
        int i = 0, j = 0;
        int k = l;
        while (i < n1 && j < n2)
        {
            if (L[i]<=R[j])
            {
                arr[k] = L[i];
                i++;
            }
            else
            {
                arr[k] = R[j];
                j++;
            }
            k++;
        }
        while (i < n1)
        {
            arr[k] = L[i];
            i++;
            k++;
        }
        while (j < n2)
        {
            arr[k] = R[j];
            j++;
            k++;
        }
    }
    void sort1(int arr[], int l, int r)
    {
        if (l < r)
        {
            int m = (l+r)/2;
            sort1(arr, l, m);
            sort1(arr , m+1, r);
            merge1(arr, l, m, r);
        }
    }
    void merge3(int arr[],int arr1[],int arr2[], int l, int m, int r)
    {
        int n1 = m - l + 1;
        int n2 = r - m;
        int L[] = new int [n1];
        int R[] = new int [n2];
        int L1[]=new int[n1];
        int R1[]=new int[n2];
        int L2[]=new int[n1];
        int R2[]=new int[n2];
        //long L3[]=new long[n1];
        //long R3[]=new long[n2];
        for (int i=0; i<n1; ++i)
        {
            L[i] = arr[l + i];
            L1[i]=arr1[l+i];
            L2[i]=arr2[l+i];
            //L3[i]=arr3[l+i];
        }
        for (int j=0; j<n2; ++j)
        {
            R[j] = arr[m + 1+ j];
            R1[j]=arr1[m+1+j];
            R2[j]=arr2[m+1+j];
            //R3[j]=arr3[m+1+j];
        }
        int i = 0, j = 0;
        int k = l;
        while (i < n1 && j < n2)
        {
            if (L[i] <= R[j])
            {
                arr[k] = L[i];
                arr1[k]=L1[i];
                arr2[k]=L2[i];
                //arr3[k]=L3[i];
                i++;
            }
            else
            {
                arr[k] = R[j];
                arr1[k]=R1[j];
                arr2[k]=R2[j];
                //arr3[k]=R3[j];
                j++;
            }
            k++;
        }
        while (i < n1)
        {
            arr[k] = L[i];
            arr1[k]=L1[i];
            arr2[k]=L2[i];
            //arr3[k]=L3[i];
            i++;
            k++;
        }
        while (j < n2)
        {
            arr[k] = R[j];
            arr1[k]=R1[j];
            arr2[k]=R2[j];
            //arr3[k]=R3[j];
            j++;
            k++;
        }
    }
    void sort3(int arr[],int arr1[],int arr2[], int l, int r)
    {
        if (l < r)
        {
            int m = (l+r)/2;
            sort3(arr,arr1,arr2, l, m);
            sort3(arr ,arr1,arr2, m+1, r);
            merge3(arr,arr1,arr2,l, m, r);
        }
    }
    void merge2(long arr[],long arr1[],int l, int m, int r)
    {
        int n1 = m - l + 1;
        int n2 = r - m;
        long L[] = new long [n1];
        long R[] = new long [n2];
        long L1[]=new long[n1];
        long R1[]=new long[n2];
        for (int i=0; i<n1; ++i)
        {
            L[i] = arr[l + i];
            L1[i]=arr1[l+i];
        }
        for (int j=0; j<n2; ++j)
        {
            R[j] = arr[m + 1+ j];
            R1[j]=arr1[m+1+j];
        }
        int i = 0, j = 0;
        int k = l;
        while (i < n1 && j < n2)
        {
            if (L[i] <= R[j])
            {
                arr[k] = L[i];
                arr1[k]=L1[i];
                i++;
            }
            else
            {
                arr[k] = R[j];
                arr1[k]=R1[j];
                j++;
            }
            k++;
        }
        while (i < n1)
        {
            arr[k] = L[i];
            arr1[k]=L1[i];
            i++;
            k++;
        }
        while (j < n2)
        {
            arr[k] = R[j];
            arr1[k]=R1[j];
            j++;
            k++;
        }
    }
    void sort2(long arr[],long arr1[],int l, int r)
    {
        if (l < r)
        {
            int m = (l+r)/2;
            sort2(arr,arr1, l, m);
            sort2(arr ,arr1, m+1, r);
            merge2(arr,arr1,l, m, r);
        }
    }
    void merge4(int arr[],int arr1[],int arr2[],int arr3[], int l, int m, int r)
    {
        int n1 = m - l + 1;
        int n2 = r - m;
        int L[] = new int [n1];
        int R[] = new int [n2];
        int L1[]=new int[n1];
        int R1[]=new int[n2];
        int L2[]=new int[n1];
        int R2[]=new int[n2];
        int L3[]=new int[n1];
        int R3[]=new int[n2];
        for (int i=0; i<n1; ++i)
        {
            L[i] = arr[l + i];
            L1[i]=arr1[l+i];
            L2[i]=arr2[l+i];
            L3[i]=arr3[l+i];
        }
        for (int j=0; j<n2; ++j)
        {
            R[j] = arr[m + 1+ j];
            R1[j]=arr1[m+1+j];
            R2[j]=arr2[m+1+j];
            R3[j]=arr3[m+1+j];
        }
        int i = 0, j = 0;
        int k = l;
        while (i < n1 && j < n2)
        {
            if (L[i] <= R[j])
            {
                arr[k] = L[i];
                arr1[k]=L1[i];
                arr2[k]=L2[i];
                arr3[k]=L3[i];
                i++;
            }
            else
            {
                arr[k] = R[j];
                arr1[k]=R1[j];
                arr2[k]=R2[j];
                arr3[k]=R3[j];
                j++;
            }
            k++;
        }
        while (i < n1)
        {
            arr[k] = L[i];
            arr1[k]=L1[i];
            arr2[k]=L2[i];
            arr3[k]=L3[i];
            i++;
            k++;
        }
        while (j < n2)
        {
            arr[k] = R[j];
            arr1[k]=R1[j];
            arr2[k]=R2[j];
            arr3[k]=R3[j];
            j++;
            k++;
        }
    }
    void sort4(int arr[],int arr1[],int arr2[],int arr3[], int l, int r)
    {
        if (l < r)
        {
            int m = (l+r)/2;
            sort4(arr,arr1,arr2,arr3, l, m);
            sort4(arr ,arr1,arr2,arr3, m+1, r);
            merge4(arr,arr1,arr2,arr3,l, m, r);
        }
    }
    public int justsmall(int a[],int l,int r,int x)
    {
        int p=-1;
        while(l<=r)
        {
            int mid=(l+r)/2;
            if(a[mid]<=x)
            {
                p=mid;
                l=mid+1;
            }
            else
                r=mid-1;
        }
        return p;
    }
    public int justlarge(int a[],int l,int r,int x)
    {
        int p=0;
        while(l<=r)
        {
            int mid=(l+r)/2;
            if(a[mid]<=x)
            {
                l=mid+1;
            }
            else
            {
                p=a[mid];
                r = mid - 1;
            }
        }
        return p;
    }
    long gcd(long x,long y)
    {
        if(x%y==0)
            return y;
        else
            return(gcd(y,x%y));
    }
    long fact(long n)
    {
        long ans=1;
        for(int i=1;i<=n;i++)
            ans*=i;
        return ans;
    }
    public static void main(String args[])throws Exception
    {
        new Thread(null,new templ(),"templ",1<<26).start();
    }
    public void run() {
        try
        {
            InputReader in = new InputReader(System.in);
            PrintWriter out = new PrintWriter(System.out);
            int l=in.ni();
            String s1=in.nextLine();
            String s2=in.nextLine();
            char c1[]=new char[l+1];
            char c2[]=new char[l+1];
            for(int i=1;i<=l;i++)
            {
                c1[i]=s1.charAt(i-1);
                c2[i]=s2.charAt(i-1);
            }
            int k=0;
            for(int i=1;i<=l/2;i++)
            {
                char p=c1[i];
                char q=c1[l-i+1];
                char r=c2[i];
                char s=c2[l-i+1];
                HashSet<Character> hs=new HashSet<>();
                hs.add(p);
                hs.add(q);
                hs.add(r);
                hs.add(s);
                if(hs.size()==4)
                    k+=2;
                if(hs.size()==3)
                {
                    if(p==q)
                        k+=2;
                    else
                        k+=1;
                }
                if(hs.size()==2)
                {
                    HashMap<Character,Integer>hm=new HashMap<>();
                    hm.put(p,1);
                    if(hm.containsKey(q))
                    {
                        int kk=hm.get(q);
                        hm.put(q,kk+1);
                    }
                    else
                        hm.put(q,1);
                    if(hm.containsKey(r))
                    {
                        int kk=hm.get(r);
                        hm.put(r,kk+1);
                    }
                    else
                        hm.put(r,1);
                    if(hm.containsKey(s))
                    {
                        int kk=hm.get(s);
                        hm.put(s,kk+1);
                    }
                    else
                        hm.put(s,1);
                    if(hm.get(p)%2==1)
                        k+=1;
                }
            }
            if(l%2==1&&c1[l/2+1]!=c2[l/2+1])
                k++;
            out.println(k);
            out.close();
        }
        catch(Exception e){
            return;
        }
    }
    static class InputReader {

        private final InputStream stream;
        private final byte[] buf = new byte[8192];
        private int curChar, snumChars;

        public InputReader(InputStream stream) {
            this.stream = stream;
        }

        public int read() {
            if (snumChars == -1)
                throw new InputMismatchException();
            if (curChar >= snumChars) {
                curChar = 0;
                try {
                    snumChars = stream.read(buf);
                } catch (IOException e) {
                    throw new InputMismatchException();
                }
                if (snumChars <= 0)
                    return -1;
            }
            return buf[curChar++];
        }

        public int ni() {
            int c = read();
            while (isSpaceChar(c)) {
                c = read();
            }
            int sgn = 1;
            if (c == '-') {
                sgn = -1;
                c = read();
            }
            int res = 0;
            do {
                res *= 10;
                res += c - '0';
                c = read();
            } while (!isSpaceChar(c));
            return res * sgn;
        }

        public long nl() {
            int c = read();
            while (isSpaceChar(c)) {
                c = read();
            }
            int sgn = 1;
            if (c == '-') {
                sgn = -1;
                c = read();
            }
            long res = 0;
            do {
                res *= 10;
                res += c - '0';
                c = read();
            } while (!isSpaceChar(c));
            return res * sgn;
        }

        public int[] nextIntArray(int n) {
            int a[] = new int[n];
            for (int i = 0; i < n; i++) {
                a[i] = ni();
            }
            return a;
        }

        public String readString() {
            int c = read();
            while (isSpaceChar(c)) {
                c = read();
            }
            StringBuilder res = new StringBuilder();
            do {
                res.appendCodePoint(c);
                c = read();
            } while (!isSpaceChar(c));
            return res.toString();
        }

        public String nextLine() {
            int c = read();
            while (isSpaceChar(c))
                c = read();
            StringBuilder res = new StringBuilder();
            do {
                res.appendCodePoint(c);
                c = read();
            } while (!isEndOfLine(c));
            return res.toString();
        }

        public boolean isSpaceChar(int c) {
            return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1;
        }

        private boolean isEndOfLine(int c) {
            return c == '\n' || c == '\r' || c == -1;
        }

    }
}