#include <bits/stdc++.h>

using namespace std;

#define REP(i,n) for(int i=0; i<(int)(n); i++)
#define FOR(i,b,e) for (int i=(int)(b); i<(int)(e); i++)
#define ALL(x) (x).begin(), (x).end()

const double PI = acos(-1);

int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);

  string s;
  cin >> s;
  map<char, int> cnt;
  for (char c: s) cnt[c]++;
  
  if (cnt.size() == 13) {
    for (char c = 'a'; c <= 'm'; c++)
      cout << c << endl;
  } else if (cnt.size() == 12) {
    for (char c = 'a'; c <= 'm'; c++)
      if (!cnt[c])
        cout << c << endl;
  } else {
    cout << "Impossible" << endl;
  }

  return 0;
}