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#include<cstdio>
#include<utility>
#include<vector>

typedef std::pair<int, int> pii;
typedef std::vector<pii> vpii;
typedef long long ll;

int n;
vpii v;

void input() {
  scanf("%d", &n);
  int a;
  int last = 0;
  for (int i = 0; i < n; i++) {
    scanf("%d", &a);
    if (a != 0) {
      v.push_back(std::make_pair(i - last, a));
      last = i;
      // printf("%d %d\n", v[v.size() - 1].first, v[v.size() - 1].second);
    }
  }
}

int min(int & a, int & b) {
  return a < b ? a : b;
}

int solve(int i, ll curr, int len) {
  pii p = v[i];
  if (i == v.size()) {
    if (curr < 0) {
      return -1;
    }
    return len;
  }

  if (curr < 0) {
    return solve(i + 1, curr + p.second, len + p.first);
  }

  int s1 = solve(i + 1, p.second, len);
  int s2 = solve(i + 1, curr + p.second, len + p.first);
  if (s1 < 0) {
    return s2;
  } else if (s2 < 0) {
    return s1;
  }
  return min(s1, s2);
}

int solve() {
  return solve(0, 0ll, 0);
}

int main() {
  input();
  printf("%d\n", solve());
}