#include <iostream>
#include <vector>
using namespace std;

int main(){
    int n;
    cin >> n;
    vector<int> a(n);
    for(auto &p: a) cin >> p;
    vector<int> memo(n, -1);
    if(a[n-1] == 0) memo[n-1] = n-1;
    for(int i = n-2; i >= 0; i--){
        memo[i] = memo[i+1];
        if(a[i] == 0) memo[i] = i;
    }

    long long int ans = 0;
    for(int i = 0; i < n; i++){
        if(memo[i] != -1){
            ans += n-memo[i];
        }
    }
    cout << ans << endl;
    return 0;
}