#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using P = pair<int,int>;
#define rep(i, n) for(int i = 0; i < n; i++)
#define all(x) (x).begin(),(x).end()

int main(){
    int n;
    cin >> n;
    ll ans = 0, pls[] = {0,0};
    rep(i,n-1){
        int a;
        cin >> a;
        if(!a){
            pls[i%2] = 0;
            ans += pls[!(i%2)];
        }
        else{
            pls[!(i%2)] = 0;
            ans += ++pls[i%2];
        }
    }
    cout << ans << endl;
    return 0;
}