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 count = 0;
        for(int a0 = 0; a0 < n; a0++){
            int x = in.nextInt();
            int y = in.nextInt();
            int z= 0;
            if(y<0){
                z = -1*Integer.parseInt(Integer.toString(x) + Integer.toString(y*-1));
            }else{
                z = Integer.parseInt(Integer.toString(x) + Integer.toString(y));
            }
            
            if (x > n || y > n || z > n){
                count = count+1;
            }
        }
        if(count == 0){
            System.out.println("YES");
        } else {
            System.out.println("NO");
        }
    }
}