Given N and N elements Find the number of distinct sums

DistinctSum.java

/* package codechef; // don't place package name! */

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

/* Name of the class has to be "Main" only if the class is public. */
class Codechef
{
	public static void main (String[] args) throws java.lang.Exception
	{
		// your code goes here
		Scanner sc = new Scanner(System.in);
		int n = Integer.parseInt(sc.nextLine());
		int []a= new int[n];
		for(int i=0;i<n;i++)
		a[i]=Integer.parseInt(sc.nextLine());
		
		HashSet<Integer> hs=new HashSet<>();
		for(int i=0;i<n;i++)
	    hs.add(a[i]);
		for(int i=0;i<n;i++)
	        for(int j=i+1;j<n;j++)
	            if(!hs.contains(a[i]+a[j]))
	                hs.add(a[i]+a[j]);
	   System.out.println(hs.size());         
		
	}
}