<>;
@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;
}

($e0)=grep{$_%2==0}@d;
($e1)=grep{$_%2==1}@d;

if( $z%2 ? $z<=$e1+$e2 : $z<=$e0*2 || $z<=$e1*2 ) {
	print 2;
	exit;
}

print -1;