(defun main ()
  (let* ((n (read))
         (s (read))
         (b (read))
         (h (read))
         (m h))
    (loop for i below (1- n)
          with a = (read)
          when (> a (+ m (* b s)))
            do (progn (princ "No") (terpri) (return-from main))
          do (setq m (max m a)))
    (princ "Yes")
    (terpri)))
(main)