object Main{
 def main(args: Array[String]){
   var x:Long = io.StdIn.readLine().toLong;

   var kaisu:Long = 0L;
   var ten:Long = 0L;
   var flg:Long = 0L;

   while (ten < x){
       if (flg == 0){
           ten = ten + 6;
           flg = 1;
       } else {
           ten = ten + 5;
           flg = 0;
       }
       kaisu = kaisu + 1;
   }
   println(kaisu);
 }
}