class F:
    def __init__(self):
        self.s0 = set(chr(i) for i in range(ord('a'), ord('a')+13))
    
    def __call__(self):
        S = input()
        
        s = set(c for c in S)
        s_len = len(s)
    
        if s_len == 13 and self.s0 == s:
            for i in range(ord('a'), ord('a')+13):
                print(chr(i))
        elif s_len == 12:  
            t = self.s0.symmetric_difference(s)
            if len(t) == 1:
                print(t.pop())
            else:
                print("Impossible")
        else:
            print("Impossible")

f = F()
f()