forall aa,ab:s . aa <= ab => p
not (s(n) <= 0)
not s(n) <= 0
s(n) <= 0
i * q <= j * p
(i * q) <= (j * p)
c * (a + b) = (c * a) + (c * b)
(a + b) * c = (a * c) + (b * c)
a <= b <= c
even(A x)
even A x