#include <bits/stdc++.h>
#include <atcoder/all>
using namespace std;
using namespace atcoder;
using ll = long long;
using ld = long double;
using mint = modint998244353;

int main() {
  int N; cin >> N;
  vector<int> A(N);
  for (int i = 0; i < N; i++) cin >> A[i];
  auto B = A;
  for (int i = 1; i < N; i += 2) B[i] ^= 1;
  B.push_back(-1);
  int p = N;
  vector<int> c(N);
  for (int i = N - 1; i >= 0; i--) {
    if (B[i] != B[p]) p = i;
    c[i] = p + 1;
  }
  ll ans = 0;
  for (int i = 0; i < N; i++) if (A[i]) ans += min(c[i], N - 1) - i;
  cout << ans << endl;
  return 0;
}