import Prelude
import Data.Bool (bool)

main :: IO ()
main = do
  [x, y] <- map read . words <$> getLine
  _ <- getLine
  as <- map read . words <$> getLine
  putStrLn $ bool "NO" "YES" $ solve x y as

solve :: Int -> Int -> [Int] -> Bool
solve vx vy as = let dv = vy - vx
                   in  all (\(a, d) -> dv * a <= d * vx) $ distances as
  where
    distances :: [Int] -> [(Int, Int)]
    distances as = zip as $ zipWith (-) (tail as) as