{-# LANGUAGE BangPatterns #-}

import           Control.Monad
import           Control.Monad.Cont
import           Control.Monad.ST
import           Data.STRef.Strict
import qualified Data.Vector.Fusion.Stream.Monadic as VFSM
import qualified Data.Vector.Unboxed               as VU
import qualified Data.Vector.Unboxed.Mutable       as VUM

main :: IO ()
main = do
  n <- readLn :: IO Int
  let vec = quotientRange n
  print $ succ $ VU.length $ VU.filter (\(a, _, _) -> a /= 0) vec

quotientRange :: Int -> VU.Vector (Int, Int, Int)
quotientRange n = VU.create $ do
  ret <- VUM.unsafeNew n :: ST s (VUM.STVector s (Int, Int, Int))
  ptr <- newSTRef (0 :: Int)
  forG 1 n (^) 2 (+) 1 $ \m -> VUM.unsafeWrite ret m (m, m, n `div` m) >> modifySTRef' ptr succ
  let m = floor . sqrt . fromIntegral $ n
  rev1' m $ \i -> do
    let
      l = n `div` (i + 1) + 1
      r = n `div` i
    p <- readSTRef ptr
    (_, bb, _) <- VUM.unsafeRead ret (p - 1)
    when (l <= r && bb < l) $ do
      VUM.unsafeWrite ret p (l, r, n `div` l)
      modifySTRef' ptr succ
  return ret

rep :: Monad m => Int -> (Int -> m ()) -> m ()
rep n = flip VFSM.mapM_ (streamG 0 (n - 1) const 0 (+) 1)
{-# INLINE rep #-}

rep' :: Monad m => Int -> (Int -> m ()) -> m ()
rep' n = flip VFSM.mapM_ (streamG 0 n const 0 (+) 1)
{-# INLINE rep' #-}

rep1 :: Monad m => Int -> (Int -> m ()) -> m ()
rep1 n = flip VFSM.mapM_ (streamG 1 (n - 1) const 0 (+) 1)
{-# INLINE rep1 #-}

rep1' :: Monad m => Int -> (Int -> m ()) -> m ()
rep1' n = flip VFSM.mapM_ (streamG 1 n const 0 (+) 1)
{-# INLINE rep1' #-}

rev :: Monad m => Int -> (Int -> m ()) -> m ()
rev n = flip VFSM.mapM_ (streamRG (n - 1) 0 const 0 (-) 1)
{-# INLINE rev #-}

rev' :: Monad m => Int -> (Int -> m ()) -> m ()
rev' n = flip VFSM.mapM_ (streamRG n 0 const 0 (-) 1)
{-# INLINE rev' #-}

rev1 :: Monad m => Int -> (Int -> m ()) -> m ()
rev1 n = flip VFSM.mapM_ (streamRG (n - 1) 1 const 0 (-) 1)
{-# INLINE rev1 #-}

rev1' :: Monad m => Int -> (Int -> m ()) -> m ()
rev1' n = flip VFSM.mapM_ (streamRG n 1 const 0 (-) 1)
{-# INLINE rev1' #-}

range :: Monad m => Int -> Int -> (Int -> m ()) -> m ()
range l r = flip VFSM.mapM_ (streamG l r const 0 (+) 1)
{-# INLINE range #-}

rangeR :: Monad m => Int -> Int -> (Int -> m ()) -> m ()
rangeR r l = flip VFSM.mapM_ (streamRG r l const 0 (-) 1)
{-# INLINE rangeR #-}

forP :: Monad m => Int -> (Int -> m ()) -> m ()
forP p = flip VFSM.mapM_ (streamG 2 p (^) 2 (+) 1)
{-# INLINE forP #-}

forG :: Monad m => Int -> Int -> (Int -> Int -> Int) -> Int -> (Int -> Int -> Int) -> Int -> (Int -> m ()) -> m ()
forG l r f p g d = flip VFSM.mapM_ (streamG l r f p g d)
{-# INLINE forG #-}

forRG :: Monad m => Int -> Int -> (Int -> Int -> Int) -> Int -> (Int -> Int -> Int) -> Int -> (Int -> m ()) -> m ()
forRG r l f p g d = flip VFSM.mapM_ (streamRG r l f p g d)
{-# INLINE forRG #-}

streamG :: Monad m => Int -> Int -> (Int -> Int -> Int) -> Int -> (Int -> Int -> Int) -> Int -> VFSM.Stream m Int
streamG !l !r !f !p !g !d = VFSM.Stream step l
  where
    step x
      | f x p <= r = return $ VFSM.Yield x (g x d)
      | otherwise  = return VFSM.Done
    {-# INLINE [0] step #-}
{-# INLINE [1] streamG #-}

streamRG :: Monad m => Int -> Int -> (Int -> Int -> Int) -> Int -> (Int -> Int -> Int) -> Int -> VFSM.Stream m Int
streamRG !r !l !f !p !g !d = VFSM.Stream step r
  where
    step x
      | f x p >= l = return $ VFSM.Yield x (g x d)
      | otherwise  = return VFSM.Done
    {-# INLINE [0] step #-}
{-# INLINE [1] streamRG #-}

withBreakIO :: ((r -> ContT r IO b) -> ContT r IO r) -> IO r
withBreakIO = flip runContT pure . callCC
{-# INLINE withBreakIO #-}

withBreakST :: ((r -> ContT r (ST s) b) -> ContT r (ST s) r) -> (ST s) r
withBreakST = flip runContT pure . callCC
{-# INLINE withBreakST #-}