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