import java.util.Scanner

object Main extends App {
  val sc = new Scanner(System.in)
  val x = sc.nextLong

  val res = x / 11 * 2 + {
    x % 11 match{
      case 0 => 0
      case y if y <= 6 => 1
      case _           => 2
    }
  }

  println(res)
}