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

using namespace std;

bitset<2000002> p;

int main()
{
    freopen("ciur.in","r",stdin);
    freopen("ciur.out","w",stdout);

    int n;
    cin>>n;
    p.set();
    p[0] = p[1] = false;
    int l = sqrt(n*1.0);
    for(int i=2;i<=n;i++)
        if(p[i])
            for(int j=2;j*i<=n;j++)
            {
                p[j*i]=0;
            }
    int sol = 0;
    for(int i = 1; i <= n; i++)
        sol += p[i];
    cout<<sol;

    return 0;
}