/* -*- coding: utf-8 -*-
 *
 * 548.cc: No.548 国士無双 - yukicoder
 */

#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<cmath>
#include<iostream>
#include<string>
#include<vector>
#include<map>
#include<set>
#include<stack>
#include<list>
#include<queue>
#include<deque>
#include<algorithm>
#include<numeric>
#include<utility>
#include<complex>
#include<functional>
 
using namespace std;

/* constant */

const int N = 13;

/* typedef */

/* global variables */

int cs[N];

/* subroutines */

/* main */

int main() {
  string s;
  cin >> s;

  for (int i = 0; i < N; i++) {
    if (s[i] < 'a' || s[i] > 'm') {
      puts("Impossible");
      return 0;
    }
    cs[s[i] - 'a']++;
  }

  int zn = 0;
  for (int i = 0; i < N; i++)
    if (cs[i] == 0) zn++;

  if (zn > 1) puts("Impossible");
  else if (zn == 1)
    for (int i = 0; i < N; i++) {
      if (cs[i] == 0) {
	printf("%c\n", 'a' + i);
	break;
      }
    }
  else
    for (int i = 0; i < N; i++) printf("%c\n", 'a' + i);
	
  return 0;
}