S = input()
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}

other = 0
for i in S:
    if i in dic:
        dic[i]+=1
    else:
        other+=1
        if other==2:
            print("Impossible")
            exit(0)
zero = 0
z = ""
for i in ["a","b","c","d","e","f","g","h","i","j","k","l","m"]:
    x = dic[i]
    if x==0:
        zero+=1
        z=i
        if zero==2:
            print("Impossible")
            exit(0)

if zero==1:
    print(z)
else:
    for i in ["a","b","c","d","e","f","g","h","i","j","k","l","m"]:
        print(i)