.
                      
                                     H
                           O     O   T     O
                        T         H  O        T
                      H             T              H
                     O              H                O
                    T          ­      O                  T
                    H               T                   H
                    O           H       O             O
                     T           T       H            T
                      H           O    T            H
                        O            H              O
         ­                   T        O          T
                        ­               T