#include <bits/stdc++.h>
using namespace std;
#ifdef LOCAL
  #include "settings/debug.cpp"
#else
  #define Debug(...) void(0)
#endif
#define rep(i, n) for (int i = 0; i < (n); ++i)
using ll = long long;
using ull = unsigned long long;

int main() {
  string s;
  cin >> s;
  vector<int> cnt(26, 0);
  for (char c : s) cnt[c - 'a']++;
  int cnt0 = 0, cnt1 = 0, cnt2 = 0;
  rep(i, 26) {
    if (cnt[i] == 0) cnt0++;
    if (cnt[i] == 1) cnt1++;
    if (cnt[i] == 2) cnt2++;
  }
  if (cnt0 == 19 && cnt1 == 1) {
    rep(i, 26) if (cnt[i] == 1) cout << (char) ('a' + i) << endl;
  }
  else {
    cout << "Impossible" << endl;
  }
  return 0;
}