from collections import *

C = Counter(input())
ans = -1
two = 0
for i in range(13):
	c = chr(ord("a") + i)
	if C[c] >= 3:
		print("Impossible")
		exit()
	if C[c] == 2:
		if two == 0:
			two += 1
		else:
			print("Impossible")
			exit()
	elif C[c] == 0:
		if ans != -1:
			print("Impossible")
			exit()
		else:
			ans = c
			
if ans == -1:
	for i in range(13):
		c = chr(ord("a") + i)
		print(c)
else:
	print(ans)