#include <iostream>
using namespace std;
typedef long long ll;

int main()
{
    int n;
    cin >> n;
    ll last = 0;
    ll ans = 0;
    for(int i = 0; i < n; i++){
        int a;
        cin >> a;
        if(a == 0) last = i + 1;
        ans += last;
    }
    cout << ans << endl;
}