#include <bits/stdc++.h>

using namespace std;

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

  int cnt[26] = {};
  for (int i = 0; i < s.size(); i++) {
    cnt[s[i] - 'a']++;
  }

  int one = 0, two = 0;
  for (int i = 0; i < 13; i++) {
    one += cnt[i] == 1;
    two += cnt[i] == 2;
  }

  if (two == 1 && one == 11) {
    for (int i = 0; i < 13; i++) {
      if (cnt[i]) continue;
      cout << (char)(i + 'a') << endl;
    }
  } else if (two == 0 && one == 13) {
    for (int i = 0; i < 13; i++) {
      cout << (char)(i + 'a') << endl;
    }
  } else {
    cout << "Impossible\n";
  }

  return 0;
}