def ctdv(num):
        c = 0
        for i in range(1,n+1):
            if num % i == 0:
                c += 1
        return c 
    
def srt_by_d_v(x):
    return (ctdv(x), -x)


for _ in range(int(input())):
    n = int(input())
    l = list(map(int, input().split()))
    k = int(input())
    
    sort_arr = sorted(l , key = srt_by_d_v)  #key hishebe 2 ta jinish nibe, age count then -value,borota age ashbe karon -borota list a age dibe
    
    #print(sort_arr)
    print(sort_arr[k-1])