import java.util.*;
import java.awt.*;
import java.awt.geom.*;
import java.io.*;

public class C
{
    public static void main(String[] args)throws Exception
    {
	
	BufferedReader r = new BufferedReader
	    (new FileReader("area.txt"));
	while(true)
	    {
		int l = Integer.parseInt(r.readLine());
	
		if(l == 0)break;

		int maxX = -3000;
		int maxY = -3000;
		int minX = 3000;
		int minY = 3000;

		Polygon po = new Polygon();
		for(int i = 0; i  < l;i++)
		    {
			StringTokenizer st = new StringTokenizer(r.readLine());
			
			int x = Integer.parseInt(st.nextToken());
			int y = Integer.parseInt(st.nextToken());
			if(x < minX)minX = x;
			if(y < minY)minY = y;
			if(x > maxX)maxX = x;
			if(y > maxY)maxY = y;

			po.addPoint(x,y);
		    }

		int ans = 0;
		/*
		int[][] table = new int[maxX-minX][maxY-minY];
    		for(int i = 0;i < maxX-minX;i++)
		    table[i] = new int[maxY-minY];

    		for(int i = 0;i < maxX-minX;i++)
    		for(int j = 0;j < maxY-minY;j++)
		    table[i][j] = 0;
		*/
		/*
		for(int i = minX;i < maxX;i++)
		for(int j = minY;j < maxY;j++)
		    {
			//if(po.intersects(new Rectangle2D.Double(i,j,1,1)))
			//if(po.intersects(i,j,1,1))
			if(po.contains(i+0.5,j+0.5))
			    {
				ans++;
				//table[][]
			    }
			else
			    {
				if(po.intersects(i,j,1,1))
				    ans++;
			    }
		    }
		*/

		ans = loop(po,minX,minY,maxX,maxY);

		System.out.println(ans);

	    }
    }
	static int loop(Polygon p,int x,int y,int ex,int ey)
	    {
		if(x == ex || y == ey)return 0;
		if(x == ex-1 && y == ey-1)
		    {
			if(p.intersects(x,y,1,1))
			    return 1;
			else
			    return 0;
		    }

		    if(p.contains(x,y,ex-x,ey-y))
			return (ex-x)*(ey-y);

		    if(p.intersects(x,y,ex-x,ey-y))
			//		    else
			{
			    int xx = (x + ex) / 2;
			    int yy = (y + ey) / 2;
			    int t = 0;
			    t += loop(p,x,y,xx,yy);
			    t += loop(p,xx,y,ex,yy);
			    t += loop(p,x,yy,xx,ey);
			    t += loop(p,xx,yy,ex,ey);
			    return t;
			}

		return 0;



	    }


 



}