#include <bits/stdc++.h>
using namespace std;

int main() {
  int N;
  cin >> N;
  int64_t ans = 0;
  vector<int> A(N), zero_p;

  for (int i = 0; i < N; i++) {
    cin >> A.at(i);
    if (!A.at(i))
      zero_p.push_back(i);
  }

  for (int i = 0; i < N; i++) {
    if (A.at(i)) {
      auto it = lower_bound(zero_p.begin(), zero_p.end(), i);
      if (it != zero_p.end())
        ans += N - *it;
    }
    else
      ans += N - i;
  }

  cout << ans << endl;
}