def f13():
    for i in range(ord('a'), ord('a')+13):
        print(chr(i))

def f12(s):
    t = set(chr(i) for i in range(ord('a'), ord('a')+13))
    print(t.symmetric_difference(s))

def main():
    S = input()
    s = set()

    for c in S:
        s.add(c)
    s_len = len(s)

    if s_len == 13:
        f13()
    elif s_len == 12:
        f12(s)
    else:
        print("Impossible")

main()