(defun man-or-boy (x)
 (a x (lambda () 1)
      (lambda () -1)
      (lambda () -1)
      (lambda () 1)
      (lambda () 0)))
 
(defun a (k x1 x2 x3 x4 x5)
  (labels ((b ()
             (decf k)
             (a k #'b x1 x2 x3 x4)))
    (if (<= k 0)
        (+ (funcall x4) (funcall x5))
        (b))))
 
(man-or-boy 10)