xs = input()
regal = [''.join(sorted(list('abcdefghijklm' + chr(c)))) for c in range(ord('a'), ord('m')+1)]
ans = []
for c in range(ord('a'), ord('m')+1):
    s = ''.join(sorted(list(xs + chr(c))))
    if s in regal: ans.append(chr(c))

if ans == []:
    print('Impossible')
else:
    [print(c) for c in ans]