import io.{StdIn => in}

object Main extends App {
  val x = in.readLong
  val ans = if(x % 11 == 0) x / 11
            else if(x % 11 < 7) (x / 11 ) * 2 + 1
            else (x / 11 ) * 2 + 2
  println(ans)
}