Codeforces Round #428 (Div. 2) A. Arya and Bran-优快云博客

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在这个问题中，Arya 每天会找到一些糖果，并尝试在规定的天数内给 Bran 分配足够的糖果。她每天最多可以给他 8 颗糖果，并且如果当天没有分配，剩下的糖果可以留到以后的日子再分配。任务是确定 Arya 需要多少天才能给 Bran 分配至少 k 颗糖果。

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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. 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.

#include <iostream>
#include <iomanip>
#include <algorithm>
#include <cstdio>
#include <cstring>
#include <queue>
#include <deque>
#include <string>
#include <cmath>
#include <vector>
#include <utility>
#include <set>
#include <map>
#include <sstream>
#include <climits>
//#pragma comment(linker, "/STACK:1024000000,1024000000")
#define pi acos(-1.0)
#define INF 2147483647
using namespace std;
typedef long long ll;
typedef pair<int,int > P;
int k,n,i,j;
int s[105];
int main()
{
    scanf("%d%d",&n,&k);
    for(i=0; i<n; i++)
    {
        scanf("%d",&s[i]);
    }
    int num=0;
    int res=0;
    for(i=0; i<n; i++)
    {
        if(s[i]>=8)
        {
            num+=8;
            res+=s[i]-8;
        }
        else
        {
            if(s[i]+res>=8)
            {
                num+=8;
                res-=(8-s[i]);
            }
            else
            {
                num+=s[i]+res;
                res=0;
            }
        }
        if(num>=k)
        {
            printf("%d\n",i+1);
            return 0;
        }
    }
    if(num<k)
        printf("-1\n");
    return 0;
}