(define yuki476
  (let*
    (
      (n (read))
      (a (read))
      (_ (read-line))
      (s (apply + (map string->number (string-split (read-line) #\space))))
      (ans (if (equal? a (/ s n)) "YES\n" "NO\n"))
    )
    (display ans)
  )
)