//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;

    while(j<n-1)
    {   string res=v[st];
         for(int i=st+1;i<n;i++)
      {
         if(i<=n-1)
         {
             res=res+v[i];
              f--;
         }

         if(f==0)
         {  x.push_back(res);
             res=" ";
             f=k;
             st=i;
             break;
             }
      }
      j++;
    }

    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();

    }



}