#include <bits/stdc++.h>
#define int long long
#define double long double
using namespace std;
const int MOD =  1000000007;
const int INF = 1e11;
using Graph = vector<vector<int>>;

signed main(){
  string S;
  cin >> S;

  set<char> cnt;
  for( int i = 0; i < S.size(); i++ ){
    cnt.insert(S[i]);
  }
  if( cnt.size() == 13 ){
    for( char i = 'a'; i <= 'm'; i++ ) cout << i << endl;
  }else if( cnt.size() == 12 ){
    for( char i = 'a'; i <= 'm'; i++ ){
      if( !cnt.count(i) ) cout << i << endl;
    }
  }else cout << "Impossible" << endl;

}