mport java.util.Scanner;

public class SpaceReplace $\{$

public static void main$($String$[]$ args$)\{$

Scanner scnr $=$ new Scanner$($System$.$in$)$;

String firstName;

String lastName;

System.out.println$(""+$ lastName $+","+$ firstName$)$;

System.out.println$("$Invalid input format."$)$;