#include<bits/stdc++.h>
using namespace std;
#define ff       first
#define ss       second
#define MX       1000005
#define mod      1000000007
#define ll       long long
#define pb       push_back
#define pll      pair<ll,ll>
#define endl     "\n"
#define bug(a)   cerr<<#a<<" : "<<a<<endl
#define all(x)   (x).begin(),(x).end()
#define allr(x)  (x).rbegin(),(x).rend()
#define Mul(a,b) (a%mod * b%mod)%mod
#define Add(a,b) (a%mod + b%mod)%mod

int divisor[10005];

bool cmp(ll a, ll b) {
    if(divisor[a] == divisor[b])
        return a>b;
    return divisor[a] < divisor[b];
}

int main() {
    ios::sync_with_stdio(0);
    cin.tie(0); cout.tie(0);

    for(int i=1; i<=10000; i++) {
        int cnt =1;
        for(int j = 1; j <= i / 2; j++) {
            if(i%j == 0)
                cnt++;
        }

        divisor[i]=cnt;
    }

    ll t;
    cin>>t;
    while(t--) {
        ll n;
        cin>>n;
        vector<ll>v;
        for(int i=0; i<n; i++) {
            ll x; cin>>x;
            v.pb(x);
        }

        ll k;
        cin>>k;

        sort(all(v), cmp);

        cout<<v[k-1]<<endl;
    }

    return 0;
}