package yukicoder;

import java.util.ArrayList;
import java.util.Scanner;

public class N548 {
	public static void main(String[] args){
		Scanner sc = new Scanner(System.in);
		String s = sc.next();
		int[] chars = new int[13];
		char c, shortageChar = 0;
		int zeroCount = 0;
		
		for(int i = 0;i < 13;++i){
			c = s.charAt(i);
			c -= 97;
			if(c < 13){
				chars[c] += 1;
			}
		}
		
		for(int i = 0;i < 13;++i){
			if(chars[i] == 0){
				++zeroCount;
				shortageChar = (char) (97 + i);
			}
		}
		
		if(zeroCount == 0){
			for(int i = 0;i < 13;++i){
				System.out.println((char) (97 + i)); 
			}
		}else if(zeroCount == 1){
			System.out.println(shortageChar);
		}else{
			System.out.println("Impossible");
		}
	}
}