S = input()
_set = set(S)
s_len = len(_set)
can_hand = 12 <= s_len <= 13
ans = "Impossible"
if can_hand:
    tile = [chr(ord("a") + i) for i in range(13)]
    if s_len == 12:
        for t in tile:
            if not t in S:
                ans = t
                break
    else:
        ans = "\n".join(tile)
print(ans)