python C3

     object
      /    \
    B      A
    |       / \
    |    C   D
     \  /       |
       E      |
        \     /
          F

L(A) = AO
L(B) = BO
L(C) = CAO
L(D) = DAO
L(E) = E + merge(BO,CAO,BC)
     = E + B + merge(O,CAO,C)
     = EBCAO
L(F) = F + merge(EBCAO,DAO,ED)
     = F + E + merge(BCAO,DAO,D)
     = F + E + B + merge(CAO,DAO,D)
     = F + E + B + C + merge(AO,DAO,D)
     = FEBCDAO