#include <iostream>
#include <cmath>
#include <fstream>

using namespace std;

int main()
{
    int n, i,c, k=0, v[299999];

    ifstream f("ciur.in");
    ofstream g("ciur.out");

    f>>n;
    k++;
    //if (n>=2)
      // cout<<2<<" ";

    for (i = 3; i <= n; i+=2)
    {
        for (c=3; c<=sqrt(i); c++)
        {
            if ((i%c==0)&&(i!=3))
                v[i] = 1;
            else
                v[i]=0;
        }

        if (v[i] == 0)
        k++;
    }

    g<<k;



}