// 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);
}
int main()
{
    float score;
    scanf("%f", &score);
    int turn = main_turn(score);
    if (turns != -1) {
        printf("%d\n",turns);
    }
    return 0;
}