S = input().rstrip()

def is_valid(S):
    freq = [0] * 13
    for a in S:
        if a > 'm' or a < 'a':
            print("Impossible")
            return
        freq[ord(a) - ord('a')] += 1
    nzero = 0
    ntwo = 0
    t = []
    for i, f in enumerate(freq):
        if f == 0:
            nzero += 1
            t.append(chr(ord('a') + i))
        if f == 2:
            ntwo += 1
        if f >= 3:
            print("Impossible")
            return
    if (nzero == 1 and ntwo == 1):
        print(t[0])
    elif (nzero == 0 and ntwo == 0):
        print('\n'.join('abcdefghijklm'))
    else:
        print("Impossible")

is_valid(S)