(VAR x)
(RULES
  f(x) -> cond1(x > 1, x)

  cond1(TRUE, x) -> cond2(x % 2 = 0, x)
  cond1(FALSE, x) -> x

  cond2(TRUE, x) -> f(x/2)
  cond2(FALSE, x) -> f(3*x + 1)
)