s = list(input())
s.sort()
c1_list = []

for i in s:
    c1_list.append(s.count(i))

if c1_list.count(1) == 13:
    for i in range(97, 97+13):
        print(chr(i))
elif (c1_list.count(1) == 11) and (c1_list.count(2) == 2):
    for i in range(97, 97+13):
        if s.count(chr(i)) == 0:
            print(chr(i))
else:
    print('Impossible')