#!/usr/bin/env python
import fileinput
import itertools
import numpy as np
from collections import Counter

txt_input = input()
S = list(txt_input)

S.sort()

count = 0
lst =[]
letter = ''

S_unique = list(set(S))

if len(S_unique) == 7:
    dct = Counter(S)
    #print(dct)
    search_letter = 1
    for name, age in dct.items():
        if age == search_letter:
            print(name)
        else:
            pass
else:
    print('Impossible')