#include<stdio.h>
int main()
{
   float score;
   scanf("%f",&score);
   if(score < 0) 
   {
       printf("Invalid input\n");
   }
   else
   {
       int intscore = (int)score;
       int turns = intscore / 3;
       int remainder = intscore % 3;
       if (remainder ! = 0)
       {
           turns +=1;
       }
       printf("%d\n",turns);
   }
   return 0;
}