#include <iostream>
#include <vector>
#include <algorithm>
#include <math.h>
#include <map>
#include <set>

#define ALL(x) (x).begin(),(x).end()
#define RALL(x) (x).rbegin(),(x).rend()
#define REP(i,a,n) for(int i = (a);i < (n);i++)
#define PI 3.14159265359
#define MOD 1000000007

using namespace std;

int main(){
    string s,b = "abcdefghijklm";
    cin >> s;
    vector<int> a(13);
    int m = 0;
    REP(i, 0, 13){
        int index = s[i]-'a';
        if(index > 13)m = 10;
        a[index]++;
        m = max(m,a[index]);
    }
    if(m > 2)cout << "Impossible\n";
    else if(m == 2){
        REP(i, 0, 13){
            if(a[i] == 0)cout << b[i] << endl;
        }
    }
    else {
        REP(i, 0, 13){
            cout << b[i] << endl;
        }
    }
    return 0;
}