#!/usr/bin/perl
use strict;
use warnings;
my $n = <>;
my (%ux, %uy);
while (my $line = <>) {
    chomp $line;
    my ($x, $y) = split / /, $line;
    $ux{$x}++;
    $uy{$y}++;
    
    if (keys %ux > 1 && keys %uy > 1) {
        print "NO"; exit;
    }
}
print "YES";