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")