10
-2 1
2 -2
-1 -2
0 0
2 -1
0 -2
2 2
0 2
-1 -1
1 -2
 40
-8 24
2 -1
1 -18
72 -70
5 -4
-308 436
-19 40
36 -35
-178 265
-1 2
-7 30
-1 0
3 -2
200 -285
17 -16
-35 74
0 -4
-86 106
-1 4
-7 6
0 1
-5 4
-2 3
6 -5
-4 5
181 -262
76 -118
0 0
-7 18
-58 104
-5 6
-6 12
-3 4
1 0
11 -10
-86 130
-3 6
153 -236
-183 270
-33 64
 5
0 -1
0 -2
0 -3
0 -4
0 -5
 10
0 1
-1 -1
1 1
-1 0
1 -1
-2 -1
-2 2
-2 0
0 -2
0 -1
 20
-1 18
-2 5
-5 4
2 -33
9 -18
0 0
11 -22
2 0
-1 2
-4 41
1 6
1 -2
6 -12
0 1
-3 6
3 -6
3 -8
-1 4
2 -5
1 0
 10
2 1
-1 0
-2 -1
-1 1
0 2
2 -2
0 0
-2 -2
0 -2
-2 1
 20
-3 -3
0 4
-3 1
1 1
-1 2
-4 4
3 -1
-3 0
0 2
4 0
2 3
2 4
4 -3
-4 3
-1 1
1 3
-2 4
1 -2
1 -1
3 0
 3
0 0
0 -1
0 1
 10
2 1
-1 1
0 0
-3 1
-2 -3
-1 -2
-1 -1
1 2
3 -2
0 -2
 3
3 3
1 2
1 1
 4
0 0
1 0
2 0
3 0
 9
1 1
1 0
0 1
0 0
-1 0
-1 1
-1 -1
1 -1
0 -1
 7
1 1
-1 -1
1 0
0 1
-1 0
0 -1
0 0

4
 57
 4
 5
 21
 4
 10
 1
 1
 0
 2
 8
 3

import java.util.*;
import java.math.*;
import java.io.*;
import static java.lang.Math.*;
import static java.util.Arrays.*;
import static java.util.Collections.*;

public class  test  {
	
	//ArrayList<Integer> lis = new ArrayList<Integer>();
	//ArrayList<String> lis = new ArrayList<String>();
	//ArrayList<test> lis = new ArrayList<test>();
//	static long sum=0;
	
public  static void main(String[] args) {
   Scanner sc =new Scanner(System.in);
   while(sc.hasNext()){
		 // =ni(sc)
	   int n=sc.nextInt();
	   long r=0;
	   int x[]=new int[2001];
	   int y[]=new int[2001];
	   // db(s);
	   for(int t=0;t<n;t++){
		 x[sc.nextInt()+1000]++;
		 sc.nextInt();
	   }
			   
	   for(int t=1;t<2001;t++){
		   y[t]+=y[t-1]+x[t];
	   }
	   
	   for(int t=1;t<2000;t++){
		   r+= y[t-1]*x[t]*(y[2000]-y[t])  ;
	   }
	   
	 	 System.out.println(r);
}  
}

    static int ni(Scanner in){
	return in.nextInt();  
 }


    static void db(Object... os){
	         System.err.println(Arrays.deepToString(os));
 
	}

}

class pair implements Comparable<pair>{
	long v;
	long s;
		pair(long v, long s){
			this.v=v;
		    this.s=s;
		}
	  
 public int compareTo(pair x){
 	 return 0<=s-x.s? 1:-1; //����
 }

}

