from collections import Counter


def is_agari(hand: str) -> bool:
    assert len(hand) == 14
    if len(set(list(hand))) != 13:
        return False
    return True


def main():
    S = input()
    agari_elm = []
    for tsumo in "abcdefghijklm":
        if is_agari(S+tsumo):
            agari_elm.append(tsumo)
    if not agari_elm:
        print("Impossible")
        return

    print("\n".join(agari_elm))


if __name__ == "__main__":
    main()