import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
import java.util.HashMap;
import java.util.LinkedHashMap;
import java.util.Map;
import java.util.Map.Entry;
import java.util.Scanner;

public class Bilsem5 {

	public static void main(String[] args) {
		Scanner in = new Scanner(System.in);
		int koordinatSayisi = Integer.parseInt(in.nextLine());
		LinkedHashMap<Integer, Integer> koordinatListesi = new LinkedHashMap<>();
		int maxX = 0;
		int maxY = 0;
		for (int i = 0; i < koordinatSayisi; i ++) {
			ArrayList<String> raf = getListFromStrSeperatedBy(in.nextLine(), " ", true);
			koordinatListesi.put(Integer.parseInt(raf.get(0)), Integer.parseInt(raf.get(1)));
			if (Integer.parseInt(raf.get(0)) > maxX) {
				maxX = Integer.parseInt(raf.get(0));
			}
			if (Integer.parseInt(raf.get(1)) > maxY) {
				maxY = Integer.parseInt(raf.get(1));
			}
		}
		in.close();
		int[][] koordinatlar = new int[maxX + 1][maxY + 1];
		boolean first = true;
		for (Entry<Integer, Integer> entry: koordinatListesi.entrySet()) {
			if (first) {
				koordinatlar[entry.getKey()][entry.getValue()] = 3;
			} else {
				koordinatlar[entry.getKey()][entry.getValue()] = 1;
			}
		}
		CoordinateList list = new CoordinateList();
		for (Entry<Integer, Integer> entry: koordinatListesi.entrySet()) {
			double distanceFromOrigin = Math.sqrt((double) Math.pow(entry.getValue(), 2.0) + (double)Math.pow(entry.getKey(), 2.0));
			list.addCoordinate(new Coordinate(entry.getKey(), entry.getValue(), distanceFromOrigin));
		}
		list.sortList();
		koordinatListesi = new LinkedHashMap<>();
		for (int i = 0; i < list.getSize(); i++) {
			koordinatListesi.put(list.getCoordinate(i).getX(), list.getCoordinate(i).getY());
		}
		int toplamAlan = 0;
		while (!checkIfDone(koordinatlar)) {
			for (Entry<Integer, Integer> entry: koordinatListesi.entrySet()) {
				list = new CoordinateList();
				for (Entry<Integer, Integer> entry2: koordinatListesi.entrySet()) {
					if (entry.equals(entry2)) {
						continue;
					}
					double alan = (double) Math.abs(entry2.getValue() - entry.getValue()) * (double) Math.abs(entry2.getKey() - entry.getKey());
					list.addCoordinate(new Coordinate(entry2.getKey(), entry2.getValue(), alan));
				}
				list.sortList();
				for (int i = 0; i < list.getSize(); i++) {
					boolean cakisma = false;
					Coordinate end = list.getCoordinate(i);
					int startX = entry.getKey();
					int startY = entry.getValue();
					int endX = end.getX();
					int endY = end.getY();
					if (endX < startX) {
						int temp = endX;
						startX = endX;
						endX = temp;
					}
					if (endY < startY) {
						int temp = endY;
						startY = endY;
						endY = temp;
					}
					if (koordinatlar[entry.getKey()][entry.getValue()] == 2 && koordinatlar[end.getX()][end.getY()] == 2
							|| koordinatlar[entry.getKey()][entry.getValue()] == 3 && koordinatlar[end.getX()][end.getY()] == 2
							|| koordinatlar[entry.getKey()][entry.getValue()] == 2 && koordinatlar[end.getX()][end.getY()] == 3
							|| koordinatlar[entry.getKey()][entry.getValue()] == 3 && koordinatlar[end.getX()][end.getY()] == 3) {
						continue;
					}
					for (int a = startX + 1; a < endX; a++) {
						for (int b = startY + 1; b < endY; b++) {
							if (koordinatListesi.containsKey(a) && koordinatListesi.get(a).equals(b)) {
								cakisma = true;
								break;
							}
						}
						if (cakisma) {
							break;
						}
					}
					if (!cakisma) {
						System.out.println("(" + entry.getKey() + ", " + entry.getValue() + ") Eslesme (" + end.getX() + ", " + end.getY() + "): " + list.getCoordinate(i).getArea());
						toplamAlan += list.getCoordinate(i).getArea();
						if (koordinatlar[entry.getKey()][entry.getValue()] == 3 || koordinatlar[end.getX()][end.getY()] == 3) {
							koordinatlar[entry.getKey()][entry.getValue()] = 3;
							koordinatlar[end.getX()][end.getY()] = 3;
						}
						koordinatlar[entry.getKey()][entry.getValue()] = 2;
						koordinatlar[end.getX()][end.getY()] = 2;
						break;
					}
				}
			}
		}
		HashMap<Integer, Integer> unfinished;
		while ((unfinished = checkIfConnected(koordinatlar)) != null) {

		}
		System.out.println(toplamAlan);
	}

	public static boolean checkIfDone(int[][] koordinatlar) {
		boolean done = true;
		for (int i = 0; i < koordinatlar.length; i++) {
			for (int j = 0; j < koordinatlar[i].length; j++) {
				if (koordinatlar[i][j] == 1) {
					done = false;
					break;
				}
			}
			if (!done) {
				break;
			}
		}
		return done;
	}

	public static HashMap<Integer, Integer> checkIfConnected(int[][] koordinatlar) {
		boolean done = true;
		HashMap<Integer, Integer> list = new HashMap<Integer, Integer>();
		for (int i = 0; i < koordinatlar.length; i++) {
			for (int j = 0; j < koordinatlar[i].length; j++) {
				if (koordinatlar[i][j] == 2) {
					done = false;
					list.put(i, j);
				}
			}
		}
		if (done) {
			return null;
		}
		return list;
	}

	public static ArrayList<String> getListFromStrSeperatedBy(String str, String seperate, boolean trimResult) {
		ArrayList<String> list = new ArrayList<>();
		while (str.length() > 0) {
			if (str.contains(seperate)) {
				if (trimResult) {
					list.add(str.substring(0, str.indexOf(seperate)).trim());
				} else {
					list.add(str.substring(0, str.indexOf(seperate)));
				}
				str = str.substring(str.indexOf(seperate) + seperate.length());
				while (str.indexOf(seperate) == 0) {
					str = str.substring(str.indexOf(seperate) + seperate.length());
				}
			} else {
				if (trimResult) {
					list.add(str.trim());
				}
				str = "";
			}
		}
		return list;
	}

	public static class Coordinate{
		int x;
		int y;
		double area;

		public Coordinate(int x, int y, double area) {
			this.x = x;
			this.y = y;
			this.area = area;
		}
		public int getX() {
			return x;
		}
		public int getY() {
			return y;
		}
		public double getArea() {
			return area;
		}
	}

	public static class CoordinateList{
		ArrayList<Coordinate> coordinates;

		public CoordinateList() {
			coordinates = new ArrayList<>();
		}
		public void addCoordinate(Coordinate co) {
			coordinates.add(co);
		}
		public Coordinate getCoordinate(int index) {
			return coordinates.get(index);
		}
		public int getSize() {
			return coordinates.size();
		}
		public void sortList() {
			Collections.sort(coordinates, new Comparator<Coordinate>() {
				public int compare(Coordinate c1, Coordinate c2)  {
					if (c1.getArea() == c2.getArea()) {
						return 0;
					} else if (c1.getArea() > c2.getArea()) {
						return 1;
					} else {
						return -1;
					}
				}
			});
		}
	}

}