#!/usr/bin/perl

$n = <STDIN>;
chomp $n;
my $hor;
my $ver;
my $sid;
my $msg = 'YES';
for my $a0 (0..$n-1){
    $x_temp = <STDIN>;
    @x_arr = split / /,$x_temp;
    $x = $x_arr[0]; 
    chomp $x;
    $y = $x_arr[1];
    chomp $y;
    
    if($a0 == 0) {
        $ver = $x;
        $hor = $y;
    } elsif ($a0 == 1) {
        if ($ver == $x) {
            $sid = 'ver';
        } elsif ($hor == $y) {
            $sid = 'hor';
        } else {
            $msg = 'NO';
            last;
        }
    }
    
    if($sid eq 'ver') {
        if ($ver != $x) {
            $msg = 'NO';
            last;
        }
    } elsif ($sid eq 'hor') {
        if($hor != $y) {
            $msg = 'NO';
            last;
        }
    }
}
print "$msg\n";