#include <stdio.h>
int calculate_min_turns(float score) {
    int int_score = (int)score;
    int turns = int_score / 3;
    if (int_score % 3 != 0) {
        turns += 1;
    }
    return turns;
}
int main() {
    float Score;
    if (scanf("%f", &score) != 1) {
    return 1;    
    }
    int min_turns = calculate_min_turns(score);
    printf("%d\n", min_turns);
    return 0;
}