#include <bits/stdc++.h>

using namespace std;

const int N = 110;

int t;
int a[N];

int main() {
    cin >> t;

    while (t -- ) {
        int n, d;
        cin >> n >> d;
        for (int i = 1; i <= n; i ++ ) cin >> a[i];

        for (int i = 2; i <= n; i ++ )
            while (a[i] && d) {
                int t = i - 1;
                if (d >= t) {
                    a[1] ++, a[i] --;
                    d -= t;
                }
                else break;
            }

        cout << a[1] << endl;
    }

    return 0;
}