Equation Icon  (si|si) = 2 (i = 1,⋅⋅⋅ ,d − 1 ), (r|r) = 2, (si+1|si) = − 1 (i = 2,⋅⋅⋅ ,d − 1 ) (5.3 ) (r|s1) = − 1, (r|sd−2) = − 1.