#include <cstdio>
#include <math.h>
using namespace std;
bool ciur[2000000];
int n;
int main()
{
    freopen("ciur.in","r",stdin);
    freopen("ciur.out","w",stdout);
    scanf("%d",&n);

    int lim = sqrt(n);
    int pas = 2;
    int nr = 0;
    for(int pas = 2; pas < n; pas++)
        {
            for(int i = pas*2; i < n; i+= pas)
            {
                if(ciur[i] == false)
                nr++;
                ciur[i] = true;


            }

        }

    printf("%d",n-nr);


    return 0;
}