| path(H[r].nxt ' + y1, H), r ∈ H, path(H[r].nxt ' + x0, H), x0 = y1 + r0 ' + y ∨ y1 = x0 + r1 ' + x ⊦ x0 = y1, r = null, ∃ r0, y. x0 = y1 + r0 ' + y, ∃ r0, x. y1 = x0 + r0 ' + x |
x0 = y1 + r0 ' + y, path(H[r].nxt ' + y1, H), r ∈ H, path(H[r].nxt ' + x0, H) ⊦ x0 = y1, r = null, ∃ r0, y. x0 = y1 + r0 ' + y, ∃ r0, x. y1 = x0 + r0 ' + x
y1 = x0 + r1 ' + x, path(H[r].nxt ' + y1, H), r ∈ H, path(H[r].nxt ' + x0, H) ⊦ x0 = y1, r = null, ∃ r0, y. x0 = y1 + r0 ' + y, ∃ r0, x. y1 = x0 + r0 ' + x