#include <bits/stdc++.h>
#include<iostream>
#include<map>
#include<vector>
#include <algorithm>
#include<math.h>
#include <iomanip>
#include<set>
#include <numeric>
#include<string>
using ll = long long;
using namespace std;

int main()
{
    ll n, cnt = 0;
    cin >> n;
    vector<ll> a(n);
    for (int i = 0; i < n; i++) cin >> a[i];
    for (int i = 0; i < n; i++){
        if (a[i] == 0){
                cnt += n - i;
                continue;
        }
        if (a[i] == 1){
            for (int j = i; j < n; j++){
                if (a[j] == 0){
                    cnt += n-j;
                    break;
                }
            }
        }
    }
    cout << cnt << endl;
}