import java.util.*;

class Main {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        String s = in.next();

        int[] alph = new int[26];
        for(int i=0; i<s.length(); i++)
            alph[(s.charAt(i) - 'a')]++;

        int temp = 0;
        for(int i=0; i<13; i++) {
            if(alph[i] == 0) temp++;
        }

        if(temp > 2) {
            System.out.println("Impossible");
        } else if(temp == 1) {
            for(int i=0; i<13; i++) {
                if(alph[i] == 0)
                    System.out.println((char)(i+'a'));
            }
        } else {
            for(int i=0; i<13; i++)
                System.out.println((char)(i+'a'));
        }
    }
}