import java.io.*;
import java.util.*;
import java.text.*;
import java.math.*;
import java.util.regex.*;

public class Solution {

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int nPoints = sc.nextInt();
        int x = sc.nextInt();
        int y = sc.nextInt();
        int nextX = sc.nextInt();
        int nextY = sc.nextInt();
        if (x != nextX && y != nextY) {
            System.out.println("NO");
            return;
        }
        boolean isExpectingHorz = true;
        if (x == nextX) {
            isExpectingHorz = false;
        }
        for (int i = 2; i < nPoints; ++i) {
            nextX = sc.nextInt();
            nextY = sc.nextInt();
            if (isExpectingHorz) {
                if (y != nextY) {
                    System.out.println("NO");
                    return;
                }
            } else {
                if (x != nextX) {
                    System.out.println("NO");
                    return;
                }
            }
        }
        System.out.println("YES");
    }
}