.
        
                                    D
                          ­    i    i   n    i
                           n      n   e     n
                          n          r          n
             ­          e            D             e
                      r              i                 t
                     D              n                D
                     i            n       e             i
                      n          r       D            n
                       n          i      n            n
                        e       ­    n   e           e
                           r           r            r
                             D        D         D
                                i       i        i
                                   n   n   n
                                        n
                     ­                   e
                                        r