//Enunt: http://www.infoarena.ro/problema/ciur
#include <iostream>
#include <fstream>

using namespace std;
bool eprim(int n,int d)
{
    if(d>n/2)
        return 1;
    if(!(n%d))
        return 0;
    return eprim(n,1+d);
}
int main()
{
    ifstream f("ciur.in");
    ofstream g("ciur.out");
    int N,count=0;
    f>>N;
    for(int i=2;i<=N;++i)
        if(eprim(i,2))
            ++count;
    g<<count;
    f.close();
    g.close();
    return 0;
}