#include <bits/stdc++.h>
using namespace std;

#define int long long

int n, c, tot = 1500, ans = -1;

inline int read() {
	int x = 0, f = 1; char c = getchar();
	while (c < '0' || c > '9') { if (c == '-') f = -1; c = getchar(); }
	while (c >= '0' && c <= '9') x = x * 10 + c - '0', c = getchar();
	return x * f;
}

signed main() {
	n = read();
	for (int i = 1; i <= n; i++) {
		c = read(), tot += c;
		if (ans != -1 && tot >= 4000) ans = i;
	}
	printf("%d\n", ans);
	return 0;
}