#!/usr/bin/perl
use v5.14;
use warnings;

use constant DEBUG => 0;

BEGIN {
    if (DEBUG) {
        require DDP;
        DDP->import;
    }
    else {
        eval 'sub p { }';
    }
}
my $input;
if (DEBUG) {
    $input = *DATA;
}
else {
    $input = *STDIN;
}

my $nr_dots = <$input>;
my ($prev_x, $prev_y, $x, $y);
my $on_same_line = 1;

while ($nr_dots--) {
    my ($x, $y) = split ' ', <$input>;
    if (!defined($prev_x)) {
        ($prev_x, $prev_y) = ($x, $y);
    }
    else {
        if ($x != $prev_x && $y != $prev_y) {
            $on_same_line = 0;
            last;
        }
    }
}

say $on_same_line ? 'YES' : 'NO';





__DATA__
5
0 1
0 2
1 3
0 4
0 5