#include<stdio.h>
int main()
{
    float score;
    print(" ");
    scanf("%f",&score);
    if(score<0){
        printf("Invalid input\n");
    }
    else{
        int scorei=(int)score;
        int turns = (scorei+2)/3;
        printf("%d\n", turns);
    }
    return 0;
}