#include <bits/stdc++.h>

using namespace std;
typedef long long ll;

int main(){
    int counter[26] = {};
    int a, b, t;
    string c;
    a = b = t = 0;
    string s;
    cin >> s;
    for (char c : s)
        counter[c-'a']++;
    for (int i : counter){
        if (i == 2)
            a++;
        else if (i == 1){
            b++;
            c += t + 'a';
        }
        t++;
    }
        
    cout << ( (a == 6 && b == 1) ? c : "Impossible" ) << endl;
    return 0;
}