package m.shin;
import java.util.Scanner;
public class Con548 {

	public static void main(String[] args) {
		Scanner s = new Scanner(System.in);
		String str = s.nextLine();
		s.close();

		boolean ans = false;
		byte[] b = str.getBytes();
		int[] a = new int[110];
		try{
			for(int i = 0;i < 13;i++){
				a[b[i]]++;
				if(a[b[i]] > 2){
					a[111]++;
				}else if(a[b[i]] == 2 && !ans){
					ans = true;
				}else if(a[b[i]] == 2 && ans){
					a[111]++;
				}
			}
			if(ans){
				for(byte i = 97;i < 110;i++){
					if(a[i] == 0){
						byte[] b2 = {i};
						System.out.println(new String(b2));
					}
				}
			}else{
				for(byte i = 97 ;i < 110;i++){
					byte[] b2 = {i};
					System.out.println(new String(b2));
				}
			}

		}catch(Exception e){
			System.out.println("Impossible");
		}
	}

}