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#pragma GCC optimize("O3")
#define _USE_MATH_DEFINES
#include <bits/stdc++.h>

#define BOOST ios::sync_with_stdio(0); cin.tie(0); cout.tie(0)
#define FOR(a, b, c) for(int a = b; a < c; ++a)
#define PB push_back
#define MP make_pair
#define INF (int)1e9+7
#define LLINF 2e18+7
#define ALL(a) a.begin(), a.end()
#define SIZE(a) (int)a.size()

typedef unsigned long long ULL;
typedef long long LL;
typedef long double LD;

using namespace std;

//#define DEBUG
#define cerr if(0) cerr

const int H = 1 << 19;

LL DP[H << 1];

void addRange(int l, int r, LL val)
{
    l += H;
    r += H;

    while(l < r)
    {
        if(l & 1)
        {
            DP[l] += val;
            l++;
        }

        if(!(r & 1))
        {
            DP[r] += val;
            r--;
        }

        l >>= 1;
        r >>= 1;
    }

    if(l == r)
        DP[l] += val;
}

LL getVal(int v)
{
    v += H;

    LL res = 0;

    while(v)
    {
        res += DP[v];
        v >>= 1;
    }

    return res;
}

int main()
{
    #ifndef DEBUG
    BOOST;
    #endif

    LL n;
    cin >> n;

    int b = n;

    FOR(i, 1, n + 1)
    {
        LL a;
        cin >> a;

        int minn = b, maxx = n;
        int oldb = b;

        while(minn < maxx)
        {
            int z = (minn + maxx) / 2;

            LL vz = getVal(z);

            if(vz + a < 0)
                minn = z + 1;
            else
                maxx = z;
        }

        if(minn <= n and getVal(minn) + a >= 0)
        {
            if(minn == b and a >= 0)
            {
                b--;
            }
        }
        else
        {
            minn = -1;
        }
    
        cerr << "minimum is: " << minn << "\n";

        addRange(oldb, n, a);

        if(minn != -1)
        {
            LL val = getVal(minn - 1);
            if(val < 0)
            {
                addRange(minn - 1, minn - 1, -val);
            }
        }

        cerr << "DEBUG:\n";

        FOR(j, b, n + 1)
        {
            cerr << getVal(j) << "\n";
        }
        cerr << "\n";
    }

    FOR(i, b, n + 1)
    {
        if(getVal(i) >= 0)
        {
            cout << i << "\n";
            return 0;
        }
    }

    cout << -1 << "\n";
    
    return 0;
}