#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",turns);
    }
    return 0;
}