import Control.Applicative
import Control.Monad
import Data.List

main :: IO ()
main = do
    x <- readLn :: IO Int
    let (q, r) = x `divMod` 11
    case () of
        _ | r == 0    -> print $ q * 2
          | r <= 6    -> print $ q * 2 + 1
          | otherwise -> print $ q * 2 + 2