#include <fstream>
using namespace std;
ifstream in("ciur.in");
ofstream out("ciur.out");
int main()
{
    int n,base,res,p;
    in >> n;
    int nr = 0;
    if(2 <=n)
        nr++;
    for(int i = 3  ; i <= n ; i+=2)
    {
        base = 2;
        res = 1;
        p = i-1;
        while(p)
        {
            if(p&1)
                res = ((res%i)*(base%i))%i;
            base *= base%i;
            p >>=1;
        }
        if(res == 1)
            nr++;
    }
    out<<nr;
    return 0;
}