<>;
@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( $z%2 ) {
	if( grep{$z0=abs$z-$_;$z1=$z+$_;bs(0,@d0-1)}@d1 ) {
		print 2;
		exit;
	}
} else {
	if( $z<=$d0*2 || $z<=$d1*2 ) {
		print 2;
		exit;
	}
}

print -1;

sub bs {
	my($i1,$i2)=@_;
	while(1){
		if($i1>$i2){
			return 0;
		}
		my$i3=$i1+$i2>>1;
		if($d0[$i3]>$z1){
			$i1=$i3+1;
		}elsif($d0[$i3]<$z0){
			$i2=$i3-1;
		}else {
			return 1;
		}
	}
}