#include<stdio.h>
int main()
{
    int n;
    scanf("%d",&n);
    int time = 0;
    while(n>0)
    {
        if(n%3==0)
        {
            n -=3;
        }
        else
        {
            n-=2;
        }
        time++;
    }
    printf("%d\n",time);
    return 0;
}