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 xt=0,yt=0;
        int[] x=new int[10];
        int[] y=new int[10];
        int n = in.nextInt();
        int n1=n*(n-1)/2;
        for(int i = 0; i < n; i++){
             x[i] = in.nextInt();
             y[i] = in.nextInt();
            for(int j=1;j<n;j++)
                {
                if(x[i]==x[j])
                    xt++;
                if(y[i]==y[j])
                    yt++;
            }
            
            
        }
        if(xt==n1 || yt==n1)
            System.out.println("YES");
        else
            System.out.println("NO");
            
    }
}