//on the name of Allah:)
#include<bits/stdc++.h>
#define int         long long
#define Endl        "\n"
#define pi          2 * acos(0.0)
#define mod         1000000007
#define Mul(a,b)    (a%mod * b%mod)%mod
#define Add(a,b)    (a%mod + b%mod)%mod
#define all(x)      (x).begin(),(x).end()
#define allr(x)     (x).rbegin(),(x).rend()
#define gcd(x, y)   (__gcd(x, y))
#define lcm(x, y)   ((x/gcd(x, y))*y)
#define faster      cin.tie(NULL), cout.tie(NULL);
#define TC          int t ; cin>>t ; for(int i=1;i<=t;i++)
const int N = 1e6 + 7;
using namespace std;
void s()
{
    int n,k;
    cin>>n>>k;
    vector<string>v(n);
    for(int i=0; i<n; i++)cin>>v[i];

    vector<string>x;
    int f=k;



    int st=0;
    int j=0;

    for(int j=0; j<n-k; j++)
    {
        string res=v[j];
        for(int i=j+1; i<n; i++)
        {

            res=res+v[i];
            f--;


            if(f==0)
            {
               // cout<<res<<endl;
                x.push_back(res);
                res=" ";
                f=k;
                st=i;

                break;

            }
        }


    }

    if(x.size()==0 || k==0)
    {
        vector<int>ans;
        for(int i=0; i<x.size(); i++)ans.push_back(stoi(x[i]));
        int mx=*max_element(all(ans));
         cout<<mx<<endl;


        return;
    }

    vector<int>ans;
    for(int i=0; i<x.size(); i++)ans.push_back(stoi(x[i]));
    int mx=*max_element(all(ans));

    cout<<mx<<endl;





}



int32_t main()
{
    ios::sync_with_stdio(false);
    //faster
    TC
    {
        //cout<<"Case "<<i<<": ";
        s();

    }



}