import sys from collections import defaultdict def solve before for in

import sys
from collections import defaultdict


def solve():
    r = ""

    before = [i*5+1 for i in range(119)]
    count = 0
    while len(r) < 4:
        d = defaultdict(lambda: [])
        for position in before:
            print(position)
            sys.stdout.flush()

            let = input()
            d[let].append(position)
        mv = None
        for let in d.keys():
            if mv is None or len(d[mv]) > len(d[let]):
                mv = let

        r += mv
        before = [k+1 for k in d[mv]]

    count = 0
    for let in list('ABCDE'):
        if let not in r:
            r += let
            count += 1

    print(r)
    sys.stdout.flush()

tc, mc = map(int, input().split(' '))
for tnum in range(tc):

    solve()

    te = input()
    if te == 'N':
        break