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#include<bits/stdc++.h>
using namespace std;
int main(){
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  int n;
  cin >> n;
  vector<long long> a(n + 1), pref(n + 1), res(n + 1);
  for(int i = 1;i <= n;i++){
    cin >> a[i];
    pref[i] = pref[i - 1] + a[i];
    res[i] = pref[i] > 0;
    for(int j = 1;j < i;j++)
      if(res[j] && pref[i] - pref[j] >= 0)
        res[i] = max(res[i], res[j] + 1);
  }
  cout << (res[n] ? n - res[n] : -1) << '\n';
}