#include <algorithm>
#include <iostream>
#include <vector>
using namespace std;

int main() {
    string s; cin >> s;
    vector<int> cnt(13, 0);
    for (char c: s) cnt[c - 'a']++;
    int one = 0, two = 0;
    for (int ci: cnt) {
        one += ci == 1;
        two += ci == 2;
    }
    if (one == 13) {
        for (int i = 0; i < 13; i++) cout << (char)(i + 'a') << endl;
    } else if (one == 11 && two == 1) {
        for (int i = 0; i < 13; i++) if (cnt[i] == 0) {
            cout << (char)(i + 'a') << endl;
        }
    } else {
        cout << "Impossible" << endl;
    }
    return 0;
}