S = "abcdefghijklm"
I = input()
L = [0 for i in range(13)]

k = 0
for c in S:
    L[k] += I.count(c)
    k += 1

if L.count(1) == 13:
    for s in list(S):
        print(s)

elif L.count(1) == 11 and L.count(0) == L.count(2) == 1:
    print(S[L.index(0)])

else:
    print("Impossible")