#include<bits/stdc++.h>
#define sz(x) (x).size()
#define all(x) (x).begin(),(x).end()
#define rep(i,a,b) for(int i=a;i<b;i++)
#define per(i,a,b) for(int i=a;i>b;i--) 
using namespace std;

using ll = long long;

void solve() {
	int n;
	cin >> n;
	
	vector<int> a(n);
	int s = 1500;

	int ans = -2;

	rep(i, 0, n) {
		cin >> a[i];
	}
	rep(i, 0, n) {
		s += a[i];
		if(s >= 4000) {
			ans = i;
			break;
		}
	}
	
	cout << ans + 1 << "\n";
}

int main() {
	std::ios::sync_with_stdio(false);
	std::cin.tie(0);
	solve();
	return 0;
}