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