#!/bin/bash
read x;

kaisu=0
ten=0
flg=0

while [ $ten -lt $x ]
do
   if [ $flg = 0 ]; then
       ten=$(($ten+6))
       flg=1
   else
       ten=$(($ten+5))
       flg=0
   fi
   kaisu=$(($kaisu+1))
done
echo $kaisu
