#include<math.h>
int solution(vector<int> &A) {
    // write your code in C++14 (g++ 6.2.0)
    int size = (int)A.size();
    int cnt = 0, res = 0;
    for (int i = 0; i < size; i++) {
        if (A[i] == 0) {
            cnt++;
        } else {
            res += cnt;
        }
    }
    if (abs(res) > 1000000000) {
        return -1;
    }

    return res;
}