#include <iostream>
#include <math.h>
#include <fstream>
int n,i,j,k,prim,nr;
using namespace std;

int main()
{
    ifstream a("ciur.in");
    ofstream b("ciur.out");
    a>>n;
    if (n<3)
    {
        b<<"Nu exista numar prim";
    }
    else
    {
        for (i=n-1;i>=2;i--)
        {
            nr=i;
            prim=1;
            for (j=2;j<=sqrt(nr);j++)
            {
                if (i%j==0)
                {
                    prim=0;
                }
            }
            if (prim==1)
            {
                k=k+1;
            }
        }
    }
    b<<k;
}