function solution(A) {

    var sum = 0;
    var res = 0;

    for(var i = A.length -1 ; i >=0 ; i--){
        if(A[i] == 1){
            sum++;
        }else {
            res+=sum;
        }
    }
    if(res > 1000000000)
        return -1;
    return res;
}