#include<bits/stdc++.h>
using namespace std;
typedef unsigned long long ull;
#define rep(i, j, k) for (int i = (j); i <= (k); ++i)
#define per(i, j, k) for (int i = (j); i >= (k); --i)
#define sz(v) int((v).size())
#define all(v) (v).begin(),(v).end()
#define endl "\n"
#define no cout<<"NO"<<endl;
#define yes cout<<"YES"<<endl;
using ll = long long;
using pii = std::pair<int, int>;
using pll = std::pair<ll, ll>;
typedef double db;
const db eps = 1e-8;
#define inf 1e18
#define ret {cout<<-1<<endl;return;}
template<typename T> bool gmax(T &x,const T y){if(x<y)return x=y,1;return 0;}
template<typename T> bool gmin(T &x,const T y){if(y<x)return x=y,1;return 0;}
#define maxn 200003
void solve()
{
    int n,f=-1,x;ll sum=1500;
    cin>>n;
    rep(i,1,n)
    {
        cin>>x;
        sum+=x;
        if(sum>=4000&&f==-1) f=i;
    }
    cout<<f<<endl;
}
signed main()
{
	ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    cout.tie(NULL);
	int t=1;
	//cin>>t;
	while(t--)solve();
}
//循环边界
//二分l和r的范围
//数组越界
//在函数内开数组赋初值
//long long
//尽量用数学语言刻画
//从直觉到严谨分析，推导
//冷静，冷静，冷静