# coding: utf-8
import collections, copy, heapq, itertools, math, sys

sys.setrecursionlimit(10 ** 7)
INF = 10 ** 20
MOD = 10 ** 9 + 7


def II(): return int(input())
def ILI(): return list(map(int, input().split()))
def IAI(LINE): return [ILI() for __ in range(LINE)]
def IDI(): return {key: value for key, value in ILI()}


def read():
    S = str(input())
    return (S,)


def solve(S):
    d_count = collections.defaultdict(int)
    for s in S:
        d_count[s] += 1
    l_q = list("abcdefghijklm")
    l_num_0 = []
    l_num_1 = []
    l_num_2 = []
    num_other = 0
    for q in l_q:
        if d_count[q] == 0:
            l_num_0.append(q)
        elif d_count[q] == 1:
            l_num_1.append(q)
        elif d_count[q] == 2:
            l_num_2.append(q)
        else:
            num_other += 1

    ans = ""
    if num_other != 0:
        ans = "Impossible"
    else:
        if len(l_num_0) == 1 and len(l_num_2) == 1:
            ans = "".join(l_num_0)
        elif len(l_num_1) == 13:
            ans = "\n".join(sorted(l_num_1))
        else:
            ans = "Impossible"

    return ans


def main():
    params = read()
    print(solve(*params))


if __name__ == "__main__":
    main()