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 count1 = 0;
        int count2 = 0;
        int x = in.nextInt();
        int y = in.nextInt();
        for(int a0 = 0; a0 < n-1; a0++){
            if(x != in.nextInt()) count1++;
            if(y != in.nextInt()) count2++;
            if(count1>0 && count2>0) break;            
        }
        if(count1>0 && count2>0) System.out.println("NO");
        else System.out.println("YES");
    }
}