#include <bits/stdc++.h>
using namespace std;

int main()
{
	int N;
	cin >> N;
	vector<int> A( N );
	for( int i = 0; i < N; i++ ) {
		cin >> A[i];
	}
	long long ans = 0;
	int l = -1;
	for( int i = 0; i < N; i++ ) {
		if( A[i] == 0 ) l = i;
		if( l >= 0 ) ans += l + 1;
	}

	cout << ans << endl;
}