(assert (= x0 0))
(assert (= x1 -3))
(assert (= x2 -1))
(assert (= x3 -1))
(assert (= x4 2))
(assert (= x5 -4))
(assert (= x6 0))
(assert (= x7 1))
(assert (= x8 2))
(assert (= x9 3))