title: How to understand this style of K-map
body: <p>I have seen a different style of Karnaugh Map for logic design. This is the style they used:
  <img src="https://i.stack.imgur.com/2sTjl.png" alt="enter image description here"></p>
  
  <p>Anyone knows how this K-Map done? How to comprehend with this kind of map? Or how they derived from that equation from that map. The map is quite different from the common map like this: <img src="https://i.stack.imgur.com/4tS0c.gif" alt="enter image description here"></p>