#include <fstream>

using namespace std;
ifstream in("ciur.in");
ofstream out("ciur.out");
int main()
{
    int n,prim,nr=0;
    in>>n;
    for(int i=3;i<n;i=i+2)
    {
        int gasit=1;
        for(int j=3;j*j<=n;j=j+2)
        {
            if(n%j==0)
                gasit=0;
            else
                gasit=1;
        }
        if(gasit==1)
            nr=nr+1;
    }
    out<<nr;
    return 0;
}