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