#include <bits/stdc++.h>
#define rep(i,n) for (int i = 0; i < (n); i ++)
using namespace std;
typedef long long ll;
typedef pair<ll,ll> PL;
typedef pair<int,int> P;
const int INF = 1e9;
const ll MOD = 1e9 + 7;

int main() {
    string S; cin >> S;
    vector<int> alpha(13,0);
    for (char s:S){
        alpha[(int)(s - 'a')] ++;
    }
    vector<int> cnt(3,0);
    bool flag = true;
    for (int p: alpha){
        if (p >= 3){
            flag = false;
            break;
        }
        else{
            cnt[p]++;
        }
    }
    if (!flag){
        printf("Impossible\n");
        return 0;
    }
    if (cnt[2] == 1 && cnt[0] == 1){
        for (int i = 0;i < 13;i++){
            if (alpha[i] == 0){
                cout << (char)(i + 97) << endl;
            }
        }
    }
    else{
        for (int i = 97;i < 97 + 13;i++){
            cout << (char)i << endl;
        }
    }
}