alpha = "abcdefghijklm"

c = {i:0 for i in alpha}

s = input()

for i in s:
    c[i] += 1

zero = sum(v == 0 for v in c.values())
one = sum(v == 1 for v in c.values())
two = sum(v == 2 for v in c.values())

if one == 13:
    for i in alpha:
        print(i)
elif zero == 1 and one == 11 and two == 1:
    for i in range(13):
        if c[alpha[i]] == 0:
            print(alpha[i])
else:
    print("Impossible")