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