#include <bits/stdc++.h>
#include <atcoder/all>
using namespace std;
using namespace atcoder;
using ll = long long;
using ld = long double;

string S;
int cnt[13];

int main() {
  cin >> S;
  int N = S.size();
  for (int i = 0; i < N; i++) {
    cnt[S[i] - 'a']++;
  }
  bool flag2 = false;
  int count = 0;
  for (int i = 0; i < 13; i++) {
    if (cnt[i] > 2) {
      cout << "Impossible" << endl;
      return 0;
    }
    else if (!flag2 && cnt[i] == 2) flag2 = true;
    else if (flag2 && cnt[i] == 2) {
      cout << "Impossible" << endl;
      return 0;
    }
    else if (cnt[i] == 1) count++;
  }
  if (flag2 && count == 11) {
    for (int i = 0; i < 13; i++) {
      if (cnt[i] == 0) {
        cout << char('a' + i) << endl;
      }
    }
  } else if (count == 13){
    for (int i = 0; i < 13; i++) {
      if (cnt[i] == 1) {
        cout << char('a' + i) << endl;
      }
    }
  } else {
    cout << "Impossible" << endl;
  }
  return 0;
}