
   +---+---+---+   +---+---+
   |       |               |
   +---+   +---+---+---+   +
   |               |       |
   +   +---+   +---+   +---+
   |   |           |   |   |
   +   +---+   +   +   +   +
   |       |   |           |
   +---+   +   +---+---+   +
   |       |       |   |   |
   +---+   +---+   +   +   +
   |       |       |       |
   +---+---+---+---+---+---+
                            
