#include <stdio.h>
#include <fstream>
#include <iostream>
using namespace std;


int main()
{
	freopen("ciur.in", "r", stdin);
	freopen("ciur.out", "w", stdout);
	int n, tot = 0, i;
	for (scanf("%d", &n); n > 0; n--)
	{
        if (n % 2 == 1 && n > 2) {
            bool gasit = false;
            for (i = 3; i <= n / 2 && !gasit; i += 2) {
                if (n % i == 0) gasit = true;
            }
            if (!gasit) tot++;
	    }
	    else if (n == 2) tot++;
	}
	printf("%d", tot);
	return 0;
}