module Main where

import qualified Data.ByteString.Char8 as BS
import Data.Char
import Data.String
import Data.List
import Data.Maybe
import Control.Monad

main :: IO ()
main = do
  x <- fst . fromJust . BS.readInt <$> BS.getLine
  putStrLn $ solve x

solve :: Int -> String
solve x
  | x >= 30 = "Yes"
  | otherwise = "No"
