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 flag = -1;
        int arr[][] = new int[n][2];
        for(int a0 = 0; a0 < n; a0++){
            int x = in.nextInt();
            int y = in.nextInt();
            arr[a0][0] = x;
            arr[a0][1] = y;     
        }
        int p1 = arr[0][0];
        int p2 = arr[0][1];
        int hor=1,ver=1;
        for(int a0 = 1; a0 < n; a0++){
            if(flag!=0 && arr[a0][0]==p1){
                flag = 1;
                ver++;
                continue;
            }else if(flag!=1 && arr[a0][1]==p2){
                flag = 0;
                hor++;
                continue;
            }
            else{
                flag=-1;
                break;
            }
            
        }
        if(flag==1 && ver ==n){
            System.out.println("YES");
        }
        else if(flag==0 && hor==n){
            System.out.println("YES");
        }
        else{
            System.out.println("NO");
        }
        }
        
    }