main :: IO ()
main = do
  a <- getLine
  let n = read a
  let m = (n `div` 11) * 2
  let tmp = n `mod` 11
  let l = if (tmp == 0)
        then -1
        else if (tmp `mod` 6 == 0)
             then 0
             else tmp `div` 6
  putStrLn . show $ m + l + 1
