import java.util.Scanner

import scala.annotation.tailrec

object Main {
  def main(args: Array[String]): Unit = {
    val sc = new Scanner(System.in)
    val n  = BigInt(sc.nextLine())
    val (a,b)=(n/11,n%11)

    val c = if (b>6)2 else 1

    println(a*2+c)
  }
}
