#include <bits/stdc++.h>
using namespace std;
int main(){
  int N;
  cin >> N;
  vector<int> A(N);
  for (int i = 0; i < N; i++){
    cin >> A[i];
  }
  vector<int> p;
  p.push_back(-1);
  for (int i = 0; i < N; i++){
    if (A[i] == 0){
      p.push_back(i);
    }
  }
  p.push_back(N);
  int cnt = p.size();
  long long ans = (long long) N * (N + 1) / 2;
  for (int i = 0; i < cnt - 1; i++){
    int d = p[i + 1] - p[i];
    ans -= (long long) d * (d - 1) / 2;
  }
  cout << ans << endl;
}