(defparameter temp (read-from-string (concatenate 'string "(" (read-line) ")")))
(defparameter H (nth 0 temp))
(defparameter W (nth 1 temp))
(defparameter N (nth 2 temp))
(defparameter K (nth 3 temp))


(format t (if (= (mod (* H W ) N) (- K 1)) "YES~%" "NO~%"))