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 lastX = in.nextInt();
        int lastY = in.nextInt();
        boolean noX = false;
        boolean noY = false;
        for(int a0 = 0; a0 < (n - 1); a0++){
            int x = in.nextInt();
            if (lastX != x) {
                noX = true;
            }
            int y = in.nextInt();
            if (lastY != y) {
                noY = true;
            }
            if (noY && noX) {
                break;
            }
        }
        if (noY && noX) {
            System.out.println("NO");
        } else {
            System.out.println("YES");
        }
    }
}