#include<iostream>
#define int long long
using namespace std;
signed main(){
	int n;
	cin>>n;
	int sum=0;
	int ans=-1;
	for(int i=1;i<=n;i++){
		int tmp;
		cin>>tmp;
		sum+=tmp;
		if(sum>=4000){
			ans=i;
			break;
		} 
	}
	cout<<ans;
	return 0;
}