<>;
@d=sort{$b-$a}glob<>;
($x,$y)=glob<>;

if($x==0&&$y==0){
	print 0;
	exit;
}

$z=abs($x)+abs($y);
if(grep$z==$_,@d){
	print 1;
	exit;
}

($d0)=@d0=grep{$_%2==0}@d;
($d1)=@d1=grep{$_%2==1}@d;

if( $z%2 ) {
	if( grep{$z>=abs($d1-$_) && $z<=$d1+$_}@d0 ) {
		print 2;
		exit;
	}
	if( grep{$z>=abs($d0-$_) && $z<=$d0+$_}@d1 ) {
		print 2;
		exit;
	}
} else {
	if( $z<=$d0*2 || $z<=$d1*2 ) {
		print 2;
		exit;
	}
}

print -1;