#include<iostream>
#include<algorithm>
#include<vector>

using namespace std;
#define repeat(i,n)for(int i=0;i<(n);i++)

int main(){

   string S;
   cin>> S;

   vector<int> cnt(26, 0);
   for(char c: S) cnt[c-'a']++;
   for(int i=0; i<='m'-'a'; i++)if(cnt[i]>=3){
      cout<< "Impossible"<< endl;
      return 0;
   }
   int _cnt2=0;
   for(int i=0; i<='m'-'a'; i++) _cnt2+=cnt[i]==2;
   if(_cnt2>1){
      cout<< "Impossible"<< endl;
      return 0;
   }
   int _cnt1=0;
   for(int i=0; i<='m'-'a'; i++) _cnt1+=cnt[i]==1;
   if(_cnt2==0){
      if(_cnt1==S.size()){
         for(int i=0; i<='m'-'a'; i++) cout<< (char)(i+'a')<< endl;
      }else{
         cout<< "Impossible"<< endl;
      }
   }else{
      for(int i=0; i<='m'-'a'; i++)if(cnt[i]==0){
         cout<< (char)(i+'a')<< endl;
      }
   }




   return 0;
}