; ハッシュ表に予約された部屋番号と予約数のペアを書いていく
; ハッシュ表内を走査し予約数が2以上であれば都度(p1+p2)*(予約数-1)を足していく
(defun main (&rest argv)
  (declare (ignorable argv))
  (let* ((p1 (read))
         (p2 (read))
         (p (+ p1 p2))
         (n (read))
               ; https://cl-community-spec.github.io/pages/make_002dhash_002dtable.html
               ; make-hash-table &key test size rehash-size rehash-threshold ⇒ hash-table
         (tabl (make-hash-table)))
    (dotimes (_ n)
            ; https://cl-community-spec.github.io/pages/gethash.html
            ; gethash key hash-table &optional default ⇒ value, present-p
      (incf (gethash (read) tabl 0)))
                 ; https://cl-community-spec.github.io/pages/loop.html
                 ; for-as-hash ::= var [type-spec] being {each | the} {{hash-key | hash-keys} {in | of} hash-table [using (hash-value other-var)] | {hash-value | hash-values} {in | of} hash-table [using (hash-key other-var)]}
    (princ (loop for value being each hash-values of tabl
                 sum (* (1- value) p)))
    (terpri)))
(main)