s = input()
hai = "abcdefghijklm"
dic = {}

count = 0
for i in hai:
    dic[i] = 0
for i in s:
    if i not in hai:
        continue
    dic[i] += 1
    count += 1

if count < 13:
    print("Impossible")
else:
    l = list(dic.values())
    if l.count(0) == 1 and l.count(1) == 11:
        for k, v in dic.items():
            if v == 0:
                print(k)
                break
    elif l.count(1) == 13:
        print("\n".join(hai))
    else:
        print("Impossible")