def decoder():
t = int(input())
for q in range(1,t+1):
    temp = [int(x) for x in input().split()]
    l = temp[1]
    L = [int(x) for x in input().split()]
    primes = []
    temp_list = []
    ans = ""

    temp_list.append(int(L[0]/gcd(L[0],L[1])))
    for i in range(1,l):
        a = gcd(L[i],L[i-1])
        temp_list.append(int(a))

    temp_list.append(int(L[l-1])/a)

    for i in temp_list:
        if i not in primes:
            primes.append(i)

    primes.sort()
    dic = {str(primes[i]): chr(i+65) for i in range(26)}

    print("Case "+"#"+str(q)+": ", end = "")
    for i in range(0,l+1):
        print(dic[str(temp_list[i])], end = "")
    print("")