#include <bits/stdc++.h>
#include <atcoder/all>
using namespace std;
using namespace atcoder;
using ll = long long;
using ld = long double;

int main() {
  int N; cin >> N;
  vector<int> A(N + 1);
  for (int i = 1; i <= N; i++) cin >> A[i];
  ll ans = 0;
  for (int i = 1; i <= N; i++) ans += i;
  ll cnt = 0;
  for (int i = 1; i <= N; i++) {
    if (A[i] == 1) cnt++;
    else {
      for (int j = 1; j <= cnt; j++) ans -= j;
      cnt = 0;
    }
  }
  for (int j = 1; j <= cnt; j++) ans -= j;
  cout << ans << endl;
  return 0;
}