#include <bits/stdc++.h>
using namespace std;
#ifdef LOCAL
  #include "settings/debug.cpp"
  #define _GLIBCXX_DEBUG
#else
  #define Debug(...) void(0)
#endif
#define rep(i, n) for (int i = 0; i < (n); ++i)
using ll = long long;
using ull = unsigned long long;

int main() {
  int n;
  cin >> n;
  vector<int> a(n);
  rep(i, n) cin >> a[i];
  vector<int> idx(0);
  rep(i, n) if (a[i] == 0) idx.push_back(i);
  idx.push_back(n);  // sentinel
  ll ans = 0;
  rep(i, n) {
    int l = *lower_bound(idx.begin(), idx.end(), i);
    int rem = n - l;
    ans += rem;
    Debug(i, rem, l);
  }
  cout << ans << endl;
  return 0;
}