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#include <ctime>
#include <cassert>
#include <iostream>
#include <iomanip>
#include <vector>
#include <list>
#include <algorithm>
#include <map>
using namespace std;
const int MAXN = 500000;
const long long MAXA = 9223372036854775807;

#define FOR(i, n) for(int i = 0, __n = (n); i < __n; i++)

long long V[MAXN];
long long S[MAXN+2];

bool reversed(const long long &a, const long long &b) {
  return a > b;
}

int main() {
  ios_base::sync_with_stdio(0);
  int n;
  cin >> n;
  FOR(i, n) {
    cin >> V[i];
    S[i] = -MAXA;
  }
  S[0] = 0;
  S[n] = S[n+1] = -MAXA;
  long long base = 0;
  FOR (i, n) {
    auto it = upper_bound(S, S + n + 1, -base, reversed);
    // cout << V[i] << " at " << it - S << " / " << base << endl;
    if (base >= 0) {
      *it = -base; // tak naprawdę = V[i]
    }
    base += V[i];

    // FOR(j, n+2) if (S[j] > -1000000000) cout << S[j] + base << " ";
    // cout << " (" << base << ")" <<endl;
  }
  if (base < 0) cout << -1 << endl;
  else {
    auto it = upper_bound(S, S + n+1, -base, reversed);
    cout << n + 1 - (it - S) << endl;
  }
}