#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, b = -1, t;
    bool one = false;
    cin >> n;
    cnt = n*(n+1)/2;
    for (ll i = 0; i < n; i++){
        cin >> t;
        if (!one && t == 1){
            b = i;
            one = true;
            continue;
        }
        if (one && t == 0){
            cnt -= (i-b)*(i-b+1)/2;
            one = false;
        }
    }
    if (b != -1 && one) cnt -= (n-b)*(n-b+1)/2;
    cout << cnt << endl;
}