#include<iostream>
#include<fstream>
#include<math.h>
using namespace std;
bool y[2000003];
int main ()
{
    ifstream fin("ciur.in");
    ofstream out("ciur.out");

    int n;
    int c=0;
    fin>>n;

     y[2]=1;
    bool x=0;
    for(int i=3;i<n;i+=2){
        for(int j=3;j<i;j+=2){
            if(i%j==0){
                x=1;break;}
        }if(x==0)c++;x=0;
    }

    out<<c;
}