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#include <bits/stdc++.h>
using namespace std;
#define REP(i,n) for(int _n=(n), i=0;i<_n;++i)
#define FOR(i,a,b) for(int i=(a),_b=(b);i<=_b;++i)
#define FORD(i,a,b) for(int i=(a),_b=(b);i>=_b;--i)
#define TRACE(x) cerr << "TRACE(" #x ")" << endl;
#define DEBUG(x) cerr << #x << " = " << (x) << endl;
typedef long long LL; typedef unsigned long long ULL;

int read_and_solve() {
  int n; cin >> n;
  vector<LL> waste;
  waste.reserve(n);
  LL sum = 0;
  int result = 0;
  REP(i,n) {
    LL x; cin >> x;
    sum += x;
    if (sum >= 0) {
      auto it = upper_bound(waste.begin(), waste.end(), sum);
      result = n - int(it - waste.begin() + 1);
      if (it == waste.end()) {
        waste.push_back(sum);
      } else {
        *it = sum;
      }
    } else {
      result = -1;
    }
  }
  return result;
}

int main() {
  cin.tie(nullptr);
  ios::sync_with_stdio(false);

  int res = read_and_solve();
  cout << res << "\n";
}