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 temp1 = in.nextInt();
            int temp2 = in.nextInt();
        int flag=0;
        for(int a0 = 0; a0 < n-1; a0++){
           int x = in.nextInt();
           int y = in.nextInt();
            if((x ^ temp1) ==1)
            { flag=1;
             break;}
            temp1 = x;
            temp2 = y;
        }
        if(flag==1)
            System.out.println("NO");
        else
            System.out.println("YES");
        
        
    }
}