#include <bits/stdc++.h>
using namespace std;
int main() {
  int length;
  int* chain;
  cin >> length;
  chain = new int[length];
  for (int i = 0; i < length; i++) cin >> chain[i];
  int count = 0;
  for (int i = 0; i < length; i++) {
    int sum = chain[i];
    for (int j = i + 1; j < length; j++) {
      if (sum == 0) count++;
    }
  }
  cout << count;
}
