If You Are Homeless... Just Build a House (Розбір)

For a given region $h\times w$ with values b_1\le b_2\le \ldots \le b_{hw}, the answer is the sum of $|b_i-b_{med}|$, where med = \lfloor \frac{hw}{2} \rfloor. It can also be stated as the following: let's keep the set of smallest $med$ numbers $S_1