#include <bits/stdc++.h>
#define int long long int
using namespace std;
int fun(vector<int>&a,int k,int c){
for(int i=0;i<a.size();i++){
a[i]=abs(a[i]-c);
}
sort(a.begin(),a.end());
//cout<<a[k]<<" ";
return a[k];
}
main() {
// your code goes here
int t;cin>>t;
while(t--){
int n,k;
cin>>n>>k;
vector<int>a(n);
for(int i=0;i<n;i++)cin>>a[i];
int c=a[k],d=a[0];
c+=d;
// cout<<c<<" ";
if(c%2==0){cout<<c/2<<endl;continue;}
if(fun(a,k,c/2)>=fun(a,k,1+(c/2)))cout<<1+c/2<<endl;
else cout<<c/2<<endl;
}
return 0;
}
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