#include <bits/stdc++.h>
using namespace std;
#ifdef LOCAL
  #include "settings/debug.cpp"
#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() {
  cin.tie(nullptr)->sync_with_stdio(false);
  int n;
  cin >> n;
  vector<int> a(n);
  rep(i, n) cin >> a[i];
  vector dp(n, vector<int>(2, 0));
  for (int i = n - 2; i >= 0; --i) {
    dp[i][0] = a[i] ? dp[i + 1][1] + 1 : 0;
    dp[i][1] = !a[i] ? dp[i + 1][0] + 1 : 0;
  }
  ll ans = 0;
  rep(i, n) ans += dp[i][0];
  cout << ans << '\n';
  return 0;
}