#include <bits/stdc++.h>
#define rep(i, n) for (int i = 0; i < n; ++i)
typedef long long ll;
using namespace std;

int main() {
    int N;
    cin >> N;
    vector<int> A(N);
    rep(i, N) cin >> A[i];

    vector<int> d(N, N);
    for (int i = N - 1; i >= 0; --i) {
        if (A[i] == 0)
            d[i] = i;
        else if (i != N - 1)
            d[i] = d[i + 1];
    }

    ll ans = 0;
    rep(i, N) ans += N - d[i];
    cout << ans << endl;

    return 0;
}