#define _USE_MATH_DEFINES
#include <sstream> //string stream its useful!
#include<string>
#include<iostream>
#include<utility> //pair
#include <vector> // vector
#include <algorithm>    // swap,sort,binary_search
#include <functional>   // std::greater
#include <map> //map
#include<set> //set
#include<queue> //queue
#include<list> //list
#include<cmath>
#include<numeric>
#include<cassert>
#include <iomanip> //cout<<setprecision
#include <regex>
#include <ctype.h> //toupper case
#include <tuple>

typedef long long ll;
#define FOR(i,a,b) for (int i=(a);i<(b);i++)
#define REP(i,n) for (int i=0;i<(n);i++)
#define RREP(i,n) for (int i=(n)-1;i>=0;i--)
ll W = 1000000007;


using namespace std;
void omajinai() {
    cin.tie(0);
    ios::sync_with_stdio(false);
    cout<<setprecision(15);
}

class Main{
public:
    string s;
    int x[13];
    Main(){
        cin>>s;
    }
    void run(){
        fill(x,x+13,0);
        REP(i,s.size()){
            const int tt = s.at(i) - 'a';
            if(tt>=13){
                cout<<"Impossible"<<endl;
                return;
            }
            x[tt]++;
        }
        const int zerocount = count_if(x,x+13,[](int x){return x == 0;});
        const int onecount = count_if(x,x+13,[](int x){return x == 1;});
        const int twocount = count_if(x,x+13,[](int x){return x == 2;});
        
        if(zerocount == 1 && onecount == 11 && twocount == 1){
            REP(i,13){ if(x[i]  == 0){
                cout<<(char)( 'a' + i) <<endl;
                return;
            }
            }
        }
        
        
        if ( zerocount == 0 && onecount == 13 && twocount == 0){
            REP(i,13) cout<<(char)( 'a' +i) <<endl;
            return;
        }
        cout<<"Impossible"<<endl;
    }
};

#ifndef gtest
int main(){
    omajinai();
    Main().run();
    return 0;
}
#endif