{-# LANGUAGE OverloadedLists     #-}
{-# LANGUAGE OverloadedStrings   #-}
{-# LANGUAGE ScopedTypeVariables #-}

import           Control.Monad
import           Data.IORef
import           Data.Maybe
import qualified Data.Text     as T
import qualified Data.Text.IO  as T
import           GHC.Base
import           System.IO

import qualified Data.Array    as A
import qualified Data.IntMap   as I
import qualified Data.Map      as M
import qualified Data.Set      as S
import qualified Data.Vector   as V

main :: IO ()
main = grouping2

grouping2 :: IO ()
grouping2 = do
  n :: Int <- readLn
  print $ n `div `3
