#include <iostream>
#include <fstream>
bool v[2000001];
using namespace std;
ifstream fin("ciur.in");
ofstream fout("ciur.out");
void ciur(int);

int main()
{
    int n,ct=1;
    fin>>n;
    ciur(n);
    for(int i=1; i<=n; i+=2)
        if(v[i]==0)
            ct++;
    fout<<ct;
    return 0;
}
void ciur(int n)
{
    int i,j;
    v[1]=1;
    for (i=4;i<=n;i+=2) v[i]=1;
    for (i=3;i*i<=n;i+=2)
        for (j=i;i*j<=n;++j) v[i*j]=1;
}