(defun my-reduce (x y) (if (= 0 (mod x y)) (my-reduce (/ x y) y) x)) (defun max-factor-impl (x cur) (let ((next-x (my-reduce x cur))) (if (= 1 next-x) cur (max-factor-impl next-x (+ 1 cur))))) (defun max-factor (x) (max-factor-impl x 2)) (format t "~&~S~%" (max-factor 600851475143))
