S = raw_input()
count = [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0]
for i in range(0, 13):
	count[ord(S[i])-97] += 1
allone = True
for i in range(0, 13):
	if count[i] != 1:
		allone = False
		break
zerotile = ''
flag = True
for i in range(0, 13):
	if count[i] == 0:
		if zerotile != '':
			flag = False
			break
		zerotile = chr(i+97)
if allone:
	for i in range(0, 13):
		print chr(i+97)
else:
	if flag: print zerotile
	else: print 'Impossible'