import           Control.Monad
import qualified Data.ByteString.Char8 as BS
import           Data.Maybe

readInt = fst . fromJust . BS.readInt
readIntList = map readInt . BS.words
getInt = readInt <$> BS.getLine
getIntList = readIntList <$> BS.getLine

main = do
  x <- getInt
  let n = x `div` 11
      r = x `mod` 11
      ans | r == 0    = n * 2
          | r <= 6    = n * 2 + 1
          | otherwise = n * 2 + 2
  print ans