fuckyeahterminals

(defun factorial (n)                                                               
   (cond ((> n 1) (* n (factorial (- n 1))))                                       
         (t 1)))                                                                   
(defun combination (n k) (/ (factorial n) (* (factorial k) (factorial (- n k)))))
(do ((n (read *standard-input* nil) (read *standard-input* nil))                   
     (d (read *standard-input* nil) (read *standard-input* nil))) ((null n))       
     (let ((r -1) (k (abs d)) (p (/ (+ (abs d) n) 2)))                             
        (cond ((= n k) (setq r 1))                                                 
              ((not (= (mod n 2) (mod k 2))) (setq r 0))                           
               (t (setq r (combination n p))))                                     
      (format t "~A ~A-step walks end at ~A~%" r n d)))