.
                                    u
                              n   nd    n
                            d     re       d
                           r       ss         r
                          e      u    n       e
                         s       d      r       s
                          s       e     s        s
                          u       s    u       u
                            n       n d      n
                              d       r       d
                                 r           r
                                       e
                                        s
                                        s