import Control.Applicative
import Control.Monad
import qualified Data.ByteString.Char8 as B
import Data.Maybe (fromJust)
import Text.Printf
import Debug.Trace

main = do
  [x] <- getInts
  print $ (x `div` 11) * 2 + if (x `mod` 11) <= 6 then 1 else 2

-- util
getInts :: IO [Integer]
getInts = map (fst . fromJust . B.readInteger) . B.words <$> B.getLine

substr :: Int -> Int -> B.ByteString -> B.ByteString
substr b l s = B.take l $ B.drop b s
