$;=$";
@d=(-2,-2,-1,+1,+2,+2,+1,-1);
$n=<>;
for(0..$n-1){
	($x,$y)=glob<>;
	$p{$x,$y}=1<<$_;
	for$j(0..7){
		$k{$x-$d[$j+6&7],$y-$d[$j]}=1;
	}
}
@b=(0,(17)x((1<<$n)-1));
for(keys%k){
	if(!$p{$_}){
		@a=@b;
		($x,$y)=glob;
		for$j(0,2,4,6){
			$p=0;
			for(0,1){
				$p|=$p{$x+$d[$j+6&7^$_],$y+$d[$j^$_]};
			}
			if($p){
				for(0..(1<<$n)-1){
					if($b[$_|$p]>$a[$_]+1){
						$b[$_|$p]=$a[$_]+1;
					}
				}
			}
		}
	}
}
print $_<17?$_:-1 for $b[(1<<$n)-1];