#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef long double ld;
typedef pair<ll,ll> PII;
const ll mx = 3e5+10;

ll Concat(ll a, ll b) {
    ll Mul = 1;
    while(Mul <=b) Mul*=10;
    return a*Mul + b;
}

int main() {
    ios_base::sync_with_stdio(0);
    cin.tie(nullptr);
    cout.tie(nullptr);
    int t;
    cin>>t;
    while(t--) {
        ll n, k;
        cin >> n >> k;
        vector<ll> Vec(n);
        for(int i=0; i<n; i++) cin >> Vec[i];
        while(k>0 and n>1) {
            ll Max = LONG_MIN;
            int Id = -1;
            for(int i=0; i<n-1; i++) {
                ll Pair = Concat(Vec[i],Vec[i+1]);
                if(Pair > Max) {
                    Max = Pair;
                    Id = i;
                }
            }
            if(Id != -1) {
                Vec[Id] = Max;
                Vec.erase(Vec.begin() + Id + 1);
                n--;
            }
            k--;
        }

        cout<<*max_element(Vec.begin(), Vec.end())<<endl;
    }
}