#define _GLIBCXX_DEBUG
#define ll long long
#define INF 1000000000;
#define INF_B 1000000000000000000;
#include <bits/stdc++.h>
using namespace std;
using Graph = vector<vector<int>>;

int main(){
  string S; cin >> S;
vector<int> B(26, 0);
  int maxB = 0, count = 0;;
  for(int i = 0; i < (int)S.size(); i++){
    int X = S[i] - 'a';
    B[X]++;
    if(B[X] == 1) count++;
    maxB = max(maxB, B[X]);
  }
  if(!(count == 7 or maxB == 2)) cout << "Impossible" << endl;
  else{
    for(int i = 0; i < 26; i++){
      if(B[i] == 1){
        char ans = 'a' + i;
        cout << ans << endl;
      }
    }
  }
}