import bisect import copy import decimal import fractions import heapq import itertools import math import random import sys import time from collections import Counter,deque,defaultdict from functools import lru_cache,reduce from heapq import heappush,heappop,heapify,heappushpop,_heappop_max,_heapify_max def _heappush_max(heap,item): heap.append(item) heapq._siftdown_max(heap, 0, len(heap)-1) def _heappushpop_max(heap, item): if heap and item < heap[0]: item, heap[0] = heap[0], item heapq._siftup_max(heap, 0) return item from math import gcd as GCD read=sys.stdin.read readline=sys.stdin.readline readlines=sys.stdin.readlines write=sys.stdout.write S=readline().rstrip() C=list(Counter(S).values()) C.sort() if C==[1]*13: ans_lst=list("abcdefghijklm") elif C==[1]*11+[2]: for s in "abcdefghijklm": if not s in S: ans_lst=[s] else: ans_lst=["Impossible"] print(*ans_lst,sep="\n")