a = input()
s = set()
while True:
    t = a[-1] * 2
    if t not in s:
        s.add(t)
        print('?', t, flush = True)
    else:
        c = 0
        for i in range(26):
            for j in range(26):
                t = chr(i + ord('a')) + chr(j + ord('a'))
                if t[-1] * 2 in s and t not in s:
                    s.add(t)
                    print('?', t, flush = True)
                    c = 1
                    break
            if c:
                break
    b = input()
    if b[0] == '?':
        _, a = b.split()
        s.add(a)
    else:
        break