#include <iostream>
#include <fstream>
#include <math.h>
using namespace std;
ifstream f("ciur.in");
ofstream g("ciur.out");
int n,i,c,a,nr=0;
char v[1000000000];
int main ()
{
    f>>n;
    for (int(i=2);i<=n;i++)
    {
        v[i]='0';
    }
    for (int(i=2);i<=sqrt(n);i++)
    {
        if (v[i]!='1')
        {a=i*2;
        c=2;
        while (a<=n)
        {
            v[a]='1';
            c++;
            a=i*c;
        }
    } }
    for (int(i=2);i<=n;i++)
    {
        if (v[i]=='0') nr++;
    }
    g<<nr<<endl;
}