//HELP ME!
//HELP ME!
#include<bits/stdc++.h>
using namespace std;
int main()
{
int x;
cin>>x;
for(int i = 1;i<=x;i++)
{
int n;
long long s;
cin>>n;
int a[n+1];
int k;
cin>>k;
if(k0 || k>n)
{
cout<<-1<<endl;
}
else{
for(int j = 1;j<=n;j++)
{
long z;
cin>>z;
if(jk) s=z;
}
