Help me in solving ARRCONCAT problem

help
,
1

My issue

Can any one explain the problem i am unable to get it

My code

import java.util.*;
import java.lang.*;
import java.io.*;

class Codechef
{
	public static void main (String[] args) throws java.lang.Exception
	{
		// your code goes here
		Scanner sc = new Scanner(System.in);
		int a = sc.nextInt();
		for(int i=0;i<a;i++){
		    int b = sc.nextInt();
		    int c = sc.nextInt();
		    
		}
		
	}
}

Problem Link: Array Concatanation Practice Coding Problem