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 in = new Scanner(System.in);
        int n = in.nextInt();
        int currentX = 0;
        int currentY = 0;
        boolean isHorizontal = true;
        boolean isVertical = true;
        
        for(int a0 = 0; a0 < n; a0++){
            int x = in.nextInt();
            int y = in.nextInt();
            if (a0 == 0) {
                currentX = x;
                currentY = y;
                continue;
            }
            if (currentX == x && currentY == y) {
                continue;
            }else if (isHorizontal && currentX == x) {
                isHorizontal = true;
                isVertical = false;
                currentX = x;
            } else if (isVertical && currentY == y) {
                isVertical = true;
                isHorizontal = false;
                currentY = y;
            } else {
                System.out.print("NO");
                return;
            }
        }
        System.out.print("YES");
    }
}