package yukicoder;

import java.util.Arrays;
import java.util.Scanner;

public class No548 {
    public static void main(String[] args) {
        String s = new Scanner(System.in).next();
        char[] schar = s.toCharArray();
        char[] charCnt = new char[13];
        int zeroCnt = 0;
        char onlyOne = 0;

        Arrays.sort(schar);
        for(int i = 0; i < 13; i++) {
            if(schar[i] - 97 < 13) {
                charCnt[schar[i] - 97] += 1;
            }
        }

        for(int i = 0; i < 13; i++) {
            if(charCnt[i] == 0) {
                zeroCnt++;
                onlyOne = (char)(i + 97);
            }
        }

        if(zeroCnt == 0) {
            for(int i = 0; i < 13; i++) {
                System.out.println((char)(97 + i));
            }
        } else if(zeroCnt == 1) {
            System.out.println(onlyOne);
        } else {
            System.out.println("Impossible");
        }
    }
}