#include<stdio.h>
#include<math.h>
int mturns(int score)
{
    if (score<-1)
    int turns=0;
    while (score>0)
        if (score>=3)
           score -=3;
           else if(score==2)
           score -=2;
           else 
           score -=1;
           turns++;
           return turns;
}
int main ()
{
    int score;
    scanf("%d",&score);
     int result =mturns(score);
     if  (result==-1)
     printf("Invalid Input\n");
     else
     printf("%d\n",result);
     return 0;
}