#include <iostream>
#include <vector>

typedef long long ll;
using namespace std;

template<typename H>
void print(H head) { cout << head << endl; }

int main()
{
  ll N;
  cin >> N;

  std::vector<ll> va(N);
  for (auto& a : va) cin >> a;

  ll cnt = 0LL;
  ll l = 0LL;
  ll r = 0LL;
  for (ll i = 0; i < N; i++) {
    if (va[i] == 1) {
      r = i;
    }

    if (va[i] == 0 || i == N-1) {
      ll n = r - l + 1;
      cnt += n * (n+1) / 2;
      l = i+1;
      r = i+1;
    }
  }

  ll ans = N * (N+1) / 2 - cnt;
  print(ans);
  return 0;
}