#include <bits/stdc++.h>
using namespace std;

bool check(string s) {
    map<char, int> m;
    for (int i = 0; i < s.size(); i++) {
        m[s[i]] += 1;
    }
    for (char c = 'a'; c <= 'm'; c++) {
        if (m[c] == 0) return false;
    }
    return true;
}

int main() {
    string S;
    cin >> S;
    bool isImpossible = true;
    for (char c = 'a'; c <= 'm'; c++) {
        if (check(S + c)) {
            cout << c << endl;
            isImpossible = false;
        }
    }
    if (isImpossible) {
        cout << "Impossible" << endl;
    }
}