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 x = in.nextInt();
        int y = in.nextInt();
        int i;
        for(i = 1; i < n; i++){
            int a=in.nextInt();
            int b=in.nextInt();
            if(a==x){continue;}
            else if(b==y){continue;}
                    else {System.out.println("NO");
                         break;}
        }
        if(i==n){System.out.println("YES");}
    }
}