#include <iostream>
#include <fstream>
#include <cmath>
#include <bitset>
using namespace std;
ifstream f("ciur.in");
ofstream g("ciur.out");

int n,c,k,i,z;
bitset <2000001> v;
int main()
{
    f>>n;
    c=sqrt(n);
    v[1]=1;
    for(i=2;i<=c;i++)
    {
        k=2;
        z=i*k;
        while(z<=n)
        {
            v[z]=1;
            k++;
            z=i*k;
        }
    }
    k=1;
    for(i=1;i<=n;i+=2)
    {
        if(v[i]==0) k++;
    }
    g<<k;
    return 0;
}