import java.util.Scanner

object Main {
  def main(args: Array[String]): Unit = {
    val N = new Scanner(System.in).nextLong()
    println(solve(N))
  }

  def solve(N: Long): Long = {
    val r = N % 11 match {
      case 0 => 0
      case r if r <= 6 => 1
      case _ => 2
    }
    (N / 11) * 2 + r
  }
}
