#include <iostream>
#include <vector>
#include <algorithm>
#define REP(i, a, n) for(ll i = ((ll) a); i < ((ll) n); i++)
#define INF 1000000000LL
#define MOD 1000000007LL
using namespace std;
typedef long long ll;

string S;
ll p[256];

int main(void) {
  cin >> S;
  REP(i, 0, 256) p[i] = 0;
  REP(i, 0, S.size()) p[S[i]]++;
  int cnt = 0;
  REP(i, 'a', 'm' + 1) if(p[i] == 0) cnt++;
  if(cnt >= 2) cout << "Impossible" << endl;
  else if(cnt == 1) {
    REP(i, 'a', 'm' + 1) if(p[i] == 0) cout << (char) i << endl;
  } else {
    REP(i, 'a', 'm' + 1) cout << (char) i << endl;
  }
}