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#include<iostream>

#define N 500001
#define B 1048576

using namespace std;

const long long linf = 1e17;
long long t[B * 2 + 1];
int n, curr;
long long pref;
const int base = B;
const int inf = N;

void tree_insert(long long pref, int res) {
  int a = res + N + base;
  if (pref < t[a]) {
    t[a] = pref;
    a /= 2;
    while (a > 0) {
      t[a] = min(t[a * 2], t[a * 2 + 1]);
      a /= 2;
    }
  }
}

int tree_find(long long pref) {
  int a = 1;
  while (a < base) {
    a *= 2;
    if (t[a] > pref) {
      a++;
    }
  }
  return a - N - base;
}

int main() {
  ios_base::sync_with_stdio(0);

  fill(t, t + base * 2 + 1, linf);

  cin >> n;
  tree_insert(0, 0);
  int prev_res = 0, res = 0;
  for (int i = 1; i <= n; i++) {
    cin >> curr;
    pref += curr;
    res = inf;
    if (pref >= 0) {
      if (curr > 0) {
        res = prev_res;
      }
      res = min(res, tree_find(pref) + i - 1);
      tree_insert(pref, res - i);
    }
    prev_res = res;
  }

  if (res == inf) {
    cout << -1 << endl;
  } else {
    cout << res << endl;
  }

  return 0;
}