solve n = 
        let 
            (q, r) = quotRem n 11
            r' = 
                if (r >= 1) && (r <= 6)
                    then 1
                    else if (r >= 7) && (r <= 10)
                        then 2
                        else 0
        in
            2 * q + r'

main = do
    n <- readLn :: IO Int
    print $ solve n