s = "abcdefghijklm"
dic = {"a":0,"b":0, "c":0, "d":0,"e":0, "f":0, "g":0,"h":0,"i":0,"j":0,"k":0,"l":0,"m":0}
S = list(input())
num, dou = 0, 0
for k in S:
    if k in dic:
        if dic[k] == 0:
            num += 1
        dic[k] += 1
        if dic[k] == 2:
            dou += 1

if num == 13:
    for i in range(13):
        print(s[i])
elif dou == 1 and num == 12:
    for i in range(13):
        if dic[s[i]] == 0:
            print(s[i])
else:
    print("Impossible")