#include<bits/stdc++.h>
using namespace std;
#define endl '\n'
#define int long long
typedef unsigned long long ull;
mt19937_64 rng(chrono::steady_clock::now().time_since_epoch().count());
const int INF = 0x7f7f7f7f7f7f;
int a[200005],sum[200005];
void solve()
{
    int n;
    cin >> n;
    int k = 1500;
    int s = -1;
    for(int i = 1;i <= n;i++)
    {
        cin >> a[i];
        k += a[i];
        if(k >= 4000 && s == -1) s = i;  
    }
    cout << s << endl;
    return;
}

signed main() 
{
    ios::sync_with_stdio(false),cin.tie(0);
    int tt;
    tt = 1;
    while(tt--)
    {
        solve();
    }
    return 0;
}