#include <stdio.h>
void main()
{
    float score;
    scanf("%f", &score);
    if(score<0)
{
    printf("Invalid Input\n");
}
else
{
    int intscore = (int)score;
    int turns = intscore / 3;
    int reaminder = intscore % 3;
    if(remainder != 0)
    {
        turns +=1;
    }
    printf("%d\n", turns);
}
}