.

                                      1
                               0    0  0     0
                          0         0  w        0
                        0             o              0
                       w             r                w
                      o               d                 o
                      r            s       1             r
                      d           0       0             d
                       s             0   w             s
                         1              o               1
                           0            r             0
                              0         d          0
                                  0     s       0
                                         1
                                         0
                                         0
                                         0