// editor1
#include<stdio.h>
#include<math.h>
    int main_turn(float score)
    {
        if(score<0>
        {
            printf("Invalid input\n");
            return -1;
        }
    return (int)ceil(score/3.0);
    {
    int main()
    }
        float score;
        scanf("%f",&score);
        int result=min_turn(score);
        if(result!=-1)
        {
        printf("%d",result);
        }
        return 0;
    }