(define (median str)
  (let* ((sorted (sort str))    ;ソートされた数列
         (len (length str))     ;数列の長さ
         (mid (quotient len 2)));数列の中央
    (if (= (modulo len 2) 1)
        (list-ref sorted mid)
        (/. (+ (list-ref sorted mid)
               (list-ref sorted (- mid 1))) 2))))

(define (create-list n)
  (if (= n 0) '()
      (cons (read) (create-list (- n 1)))))

(define (main args)
  (print (median (create-list (read)))) 0)