s = list(input())

for w in list('nopqrstuvwxyz'):
    if w in s:
        print('Impossible')
        break
else:
    count_list = []
    for e in s:
        count_list.append(s.count(e))

    if count_list.count(1) == 13:
        for e in sorted(s):
            print(e)
    elif (count_list.count(1) == 11) and (count_list.count(2) == 2):
        for w in list('abcdefghijklm'):
            if w in s:
                continue
            else:
                print(w)
                break
    else:
        print('Impossible')