#include <iostream>

using namespace std;
const int N=105;
int T;
int n,d;
int a[N];
int res;
int main()
{
    cin>>T;
    while(T--){
        cin>>n>>d;
        res=0;
        for(int i=1;i<=n;i++)
        {
            cin>>a[i];
            if(i!=1)
            {
               while(d>=(i-1)&&a[i])
               {
                   d-=(i-1);
                   a[i]--;
                   res++;
               }
            }
        }
        cout<<res+a[1]<<endl;
    }
    //cout << "Hello world!" << endl;
    return 0;
}