#include <bits/stdc++.h>
#define rep(i,n) for(int i = 0; i < (n); ++i)
#define srep(i,s,t) for (int i = s; i < t; ++i)
#define drep(i,n) for(int i = (n)-1; i >= 0; --i)
using namespace std;
typedef long long int ll;
typedef pair<int,int> P;
#define yn {puts("Yes");}else{puts("No");}
#define MAX_N 200005

int main() {
    string s;
    cin >> s;
    int a[13] = {};
    rep(i,13){
        a[s[i] - 'a']++;
    }
    int cnt = 0;
    rep(i,13){
        if(a[i] == 0)cnt++;
    }
    if(cnt >= 2){
        cout << "Impossible" << endl;
        return 0;
    }
    if(cnt == 0){
        rep(i,13){
            if(1){
                cout << (char)(i + 'a') << endl;
            }
        }
        return 0;
    }
    rep(i,13){
        if(a[i] == 0){
            cout << (char)(i + 'a') << endl;
        }
    }
    return 0;
}