(def zero (lam (f s) s))
(def succ (lam (n f s) (f (n f s))))

(def one (succ zero))
(def two (succ one))
(def three (succ two))
(def four (succ three))
(def five (succ four))

(def plus (lam (a b f s) (a f (b f s))))

(plus one three)
