#include<bits/stdc++.h>
using namespace std;
using ll = long long int;
using ld = long double;
#define pow(n,m) powl(n,m)
#define sqrt(n) sqrtl(n)
const ll MAX = 1000000000000000000;
const ll MOD = 1000000007;
//998244353;
void randinit(){srand((unsigned)time(NULL));}
int main(){
    ll N;
    cin >> N;
    vector<ll> A(N),B(N,N);
    for(ll i = 0;i < N;i++) cin >> A[i];
    for(ll i = N - 1;i >= 0;i--){
        if(i != N - 1) B[i] = B[i + 1];
        if(A[i] == 0) B[i] = i;
    }
    ll ans = 0;
    for(ll i = 0;i < N;i++) ans += N - B[i];
    cout << ans << endl;
}