.
                                   P
                           r    r   i     r
                        i        z   e       i
                     z             P            z
                    e              r               e
                  P               i                  P
                  r               z                    r
                  i             e      P               i
                  z            r         i             z
                   e            z      e              e
                    P              P                 P
                       r            i               r
                         i           z            i
                           z        e         z
                              e     P     e
                                     r
                                     i
                                     z
                                     e