reachable-n(H, n, r, r) ⊦ reachable-n(H, 0, r, r)
[[CONCRETESIMPRULES : ([CSIMPSEQ : ⊦ m * n = n * m], [CSIMPSEQ : ⊦ m0 * m * n = (m0 * m) * n], [CSIMPSEQ : ⊦ m * 0 = 0])]]