Bran and his older sister Arya are from the same house. Bran like candies so much, so Arya is going to give him some Candies.

At first, Arya and Bran have 0 Candies. There are n days, at the i-th day, Arya finds ai candies in a box, that is given by the Many-Faced God. Every day she can give Bran at most 8 of her candies. If she don't give him the candies at the same day, they are saved for her and she can give them to him later.

Your task is to find the minimum number of days Arya needs to give Bran k candies before the end of the n-th day. Formally, you need to output the minimum day index to the end of which k candies will be given out (the days are indexed from 1 to n).

Print -1 if she can't give him k candies during n given days.

Input

The first line contains two integers n and k (1 ≤ n ≤ 100, 1 ≤ k ≤ 10000).

The second line contains n integers a1, a2, a3, ..., an (1 ≤ ai ≤ 100).

Output

If it is impossible for Arya to give Bran k candies within n days, print -1.

Otherwise print a single integer — the minimum number of days Arya needs to give Bran k candies before the end of the n-th day.

Examples

Input

2 3
1 2


Output

2

Input

3 17
10 10 10


Output

3

Input

1 9
10


Output

-1

Note

In the first sample, Arya can give Bran 3 candies in 2 days.

In the second sample, Arya can give Bran 17 candies in 3 days, because she can give him at most 8 candies per day.

In the third sample, Arya can't give Bran 9 candies, because she can give him at most 8 candies per day and she must give him the candies within 1 day.
import java.util.*;
import java.io.*;
public class Main {
 
	static ArrayList<Integer> adj[];
	static char color[];
	static boolean b[],visited[],possible;
	static Map<Integer,HashSet<Integer>> s;
	static int totalnodes,colored;
	static int count[];
	static long sum[];
	public static void main(String[] args) throws IOException {
		
		
		in=new InputReader(System.in);
		w=new PrintWriter(System.out);
	   int n=in.nextInt();
	   int k=in.nextInt();
	   int[] a=new int[n];
	   for(int i=0;i<n;i++)
		   a[i]=in.nextInt();
	   int ans=0;
	   int i=0;
	   while(k>0 && i<n)
	   {
		   if(a[i]>=8)
		   {
			   k=k-8;
			   a[i]=a[i]-8;
			   if(i!=n-1)
				   a[i+1]+=a[i];
		   }
		   else 
		   {
			   k=k-a[i];
		   }
		   i++;
	   }
	  
	   if(k>0)
		   w.print(-1);
	   else
		   w.print(i);
       w.close();			
		}

	public static String[] subString(String s, int n) 
	{
	    String[] st =new String[(n*n+n)/2];
	    for(int i=0;i<st.length;i++)
	    	st[i]="";
	    int l=0;
	    for (int len = 1; len <= n; len++) 
	    {    
	        // Pick ending point
	        for (int i = 0; i <= n - len; i++) 
	        {
	            //  Print characters from current
	            // starting point to current ending
	            // point.  
	            int j = i + len - 1;            
	            for (int k = i; k <= j; k++) 
	                st[l]+=s.charAt(k);
	      //w.println(st[l]);
	            l++;
	            //cout << endl;
	        }
	    }
	    return st;
	}
	  public static long factorial(long n)
	    {
	        long res = 1, i;
	        for (i=2; i<=n; i++)
	            res *= i;
	        return res;
	    }
	
   
	public static int factors(int n,int start){
		int count = 0;
		int i;
		for(i=1;i*i<n;i++)
			if(n%i == 0){
				if(i>start)	count++;
				if(n/i > start)	count++;
			}
		if(i*i == n && i>start)	count++;
		return count;
	}


 	public static int isPrime(int n){
	    int i;

	    if (n==2)
	        return 1;

	    if (n%2==0)
	        return 0;

	    for (i=3;i<=Math.sqrt(n);i+=2)
	        if (n%i==0)
	            return 0;

	    return 1;
	}

	
	static InputReader in;
	static PrintWriter w;
	public static void seive(long n){
		b = new boolean[(int) (n+1)];
	Arrays.fill(b, true);
		for(int i = 2;i*i<=n;i++){
			if(b[i]){
				sum[i]=count[i];
			//	System.out.println(sum[i]+" wf");
				for(int p = 2*i;p<=n;p+=i){
					b[p] = false;
					sum[i]+=count[p];  
					//System.out.println(sum[i]);
				}
			}
		
		}
	}
	static class Pair implements Comparable<Pair> {
		char c;
		int count;
		public Pair(){
			
		}
		public Pair(char u, int v) {
			this.c = u;
			this.count= v;
			
		}
		public int compareTo(Pair other) {
			
				return 0;
		}
		
		/*public String toString() {
			return "[u=" + u + ", v=" + v + "]";
		}*/
	}
	static class Node2{
		Node2 left = null;
		Node2 right = null;
		Node2 parent = null;
		int data;
	}
	
	//binaryStree
	static class BinarySearchTree{
		Node2 root = null;
		int height = 0;
		int max = 0;
		int cnt = 1;
		ArrayList<Integer> parent = new ArrayList<Integer>();
		HashMap<Integer, Integer> hm = new HashMap<Integer, Integer>();
		public void insert(int x){
			Node2 n = new Node2();
			n.data = x;
			if(root==null){
				root = n;
			}
			else{
				Node2 temp = root,temp2 = null;
				while(temp!=null){
					temp2 = temp;
					if(x>temp.data) temp = temp.right;
					else temp = temp.left;
				}
				if(x>temp2.data) temp2.right = n;
				else temp2.left = n;
				n.parent = temp2;
				parent.add(temp2.data);
			}
		}
		public Node2 getSomething(int x, int y, Node2 n){
			if(n.data==x || n.data==y) return n;
			else if(n.data>x && n.data<y) return n;
			else if(n.data<x && n.data<y) return getSomething(x,y,n.right);
			else return getSomething(x,y,n.left);
		}
		public Node2 search(int x,Node2 n){
			if(x==n.data){
				max = Math.max(max, n.data);
				return n;
			}
			if(x>n.data){
				max = Math.max(max, n.data);
				return search(x,n.right);
			}
			else{
				max = Math.max(max, n.data);
				return search(x,n.left);
			}
		}
		public int getHeight(Node2 n){
			if(n==null) return 0;
			height = 1+ Math.max(getHeight(n.left), getHeight(n.right));
			return height;
		}
	}
public static void debug(Object... o) {
	System.out.println(Arrays.deepToString(o));
}
 
public static String rev(String s)
{
	StringBuilder sb=new StringBuilder(s);
	sb.reverse();
	return sb.toString();
}
 
static long lcm(long a, long b)
{
    return a * (b / gcd(a, b));
}
 
static long gcd(long a, long b)
{
    while (b > 0)
    {
        long temp = b;
        b = a % b; // % is remainder
        a = temp;
    }
    return a;
}
 
public static long max(long x, long y, long z){
		if(x>=y && x>=z) return x;
		if(y>=x && y>=z) return y;
		return z;
	}
	static int[] sieve(int n,int[] arr)
	{
	for(int i=2;i*i<=n;i++)
	{
		if(arr[i]==0)
		{
			for(int j=i*2;j<=n;j+=i)
				arr[j]=1;
		}
	}
	return arr;
	}
 
 
 
 
static class InputReader {
 
private final InputStream stream;
private final byte[] buf = new byte[8192];
private int curChar, snumChars;
private SpaceCharFilter filter;
 
public InputReader(InputStream stream) {
  this.stream = stream;
}
 
public int snext() {
  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 nextInt() {
  int c = snext();
  while (isSpaceChar(c)) {
    c = snext();
  }
  int sgn = 1;
  if (c == '-') {
    sgn = -1;
    c = snext();
  }
  int res = 0;
  do {
    if (c < '0' || c > '9')
      throw new InputMismatchException();
    res *= 10;
    res += c - '0';
    c = snext();
  } while (!isSpaceChar(c));
  return res * sgn;
}
 
public long nextLong() {
  int c = snext();
  while (isSpaceChar(c)) {
    c = snext();
  }
  int sgn = 1;
  if (c == '-') {
    sgn = -1;
    c = snext();
  }
  long res = 0;
  do {
    if (c < '0' || c > '9')
      throw new InputMismatchException();
    res *= 10;
    res += c - '0';
    c = snext();
  } while (!isSpaceChar(c));
  return res * sgn;
}
 
public int[] nextIntArray(int n) {
	 return nextIntArray(n, 0);
	    }
	    
public int[] nextIntArray(int n, int off) {
	 int[] arr = new int[n + off];
	   for (int i = 0; i < n; i++) {
	    arr[i + off] = nextInt();
	    }
	    return arr;
	    }
	    
public long[] nextLongArray(int n) {
return nextLongArray(n, 0);
	    }
        
	public long[] nextLongArray(int n, int off) {
	 long[] arr = new long[n + off];
	 for (int i = 0; i < n; i++) {
		  arr[i + off] = nextLong();
		 }
 return arr;
	}
 
 
public String readString() {
  int c = snext();
  while (isSpaceChar(c)) {
    c = snext();
  }
  StringBuilder res = new StringBuilder();
  do {
    res.appendCodePoint(c);
    c = snext();
  } while (!isSpaceChar(c));
  return res.toString();
}
 
public String nextLine() {
  int c = snext();
  while (isSpaceChar(c))
    c = snext();
  StringBuilder res = new StringBuilder();
  do {
    res.appendCodePoint(c);
    c = snext();
  } while (!isEndOfLine(c));
  return res.toString();
}
 
public boolean isSpaceChar(int c) {
  if (filter != null)
    return filter.isSpaceChar(c);
  return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1;
}
 
private boolean isEndOfLine(int c) {
  return c == '\n' || c == '\r' || c == -1;
}
 
public interface SpaceCharFilter {
  public boolean isSpaceChar(int ch);
}
}
	
}