#include<bits/stdc++.h>
typedef long long ll;
using namespace std;
int INF = 1e9;
int MOD = 1e9+7;
int cnt[13];
main(){
    string s;
    cin >> s;
    for(char c:s)if(c <= 'm')cnt[c-'a']++;
    int maxe = *max_element(cnt,cnt+13);
    if(maxe > 2){
        cout << "Impossible" << endl;
    }else if(maxe == 2){
        printf("%c\n",distance(cnt,min_element(cnt,cnt+13))+'a');
    }else{
        if(accumulate(cnt,cnt+13,0) != 13){
            cout << "Impossible" << endl;
        }else{
            for(int i = 0;i < 13;i++)printf("%c\n",i+'a');
        }
    }
}