s = input()

def check(s,e):
    import collections
    c=collections.Counter(s+e)
    if sorted(list(c.values()))!=sorted([1,1,1,1,1,1,1,1,1,1,1,1,2]):
        return False
    else:
        return True
        

for e in "abcdefghijklm":
    cnt=0
    if check(s,e)==True:
        print(e)
        cnt+=1
else:
    if cnt==0:
        print("Impossible")