#include<iostream>
using namespace std;
int kp[(int)(1e5 + 7)];
int main() {
	int cnt;
	int sheng;//
	cin >> cnt >> sheng;
	for (int i = 1; i <= cnt; i++) {
		cin >> kp[i];
	}
	int k = 0;
	for (int i = 1; i <= cnt+3; i++) {
		k++;// 1  2
		if(sheng - kp[i] <= 0){
			break;
		}
		sheng = sheng -  kp[i];
	}
	if(k<=cnt){
		cout<<k;
	}else{
		cout<<-1;
	}
	return 0;
}