A

                   A1

                               A2

                              A3

                               A4

                                                                                                 B

                                     B1

                                  B2

                                   B3

                                    B4


                                                    C

                                                              C1


                                                               C2

                                                                     C3


                                                                      C4

                            D

                                                                           D1

                        D2

                         D3

                                                                      D4

                                                                                              E



                                                             E1

                                                                E2

                                                           E3

                                                         E4

                                                                                             F

                                                                         
 
                                                                         F1

                                                                              F2

                                                                                  F3

                                                                                  F4

                                                                                F5