main :: IO ()
main = getLine >>= putStrLn . yesno . inOrder' . map read . words

inOrder' :: [Int] -> Bool
inOrder' xs = fst $ foldl (\(bool, v) x -> (bool && v <= x, x)) (True, -1) xs

yesno :: Bool -> String
yesno True = "Yes"
yesno False = "No"