#include <bits/stdc++.h>
#define rep(i, n) for (int i = 0; i < (n); i++)
using namespace std;
using ll = long long;
using pii = pair<int, int>;

int main() {
  int n;
  cin >> n;
  int pre = 0;
  ll ans = 0;
  rep(i, n) {
    int a;
    cin >> a;
    if (a == 0) {
      ans += (ll)(n - i) * (i - pre + 1);
      pre = i + 1;
    }
  }
  cout << ans << endl;
  return 0;
}