Solution:
+     +     +     +     +
                         
   0     1     1     0   
                         
+     +-----+-----+     +
      |           |      
   1  |  2     2  |  1   
      |           |      
+     +     +     +     +
      |           |      
   1  |  2     2  |  1   
      |           |      
+     +-----+-----+     +
                         
   0     1     1     0   
                         
+     +     +     +     +