#include <fstream>

using namespace std;

ifstream in("ciur.in");
ofstream out("ciur.out");

const int MAXN = 2e6;

bool c[MAXN + 2];

void ciur(int n) {
	c[0] = c[1] = 1;

	for (int i = 4; i <= n; i += 2)
		c[i] = 1;

	for (int i = 3; i * i <= n; ++ i) {
		for (int j = i * i; j <= n; j += 2 * i) {
			c[j] = 1;
		}
	}
}

int main() {
	int n;
	in >> n;
	ciur(n);
	int cnt = 1;
	for (int i = 3; i <= n; i += 2) {
		if (!c[i])
			++ cnt;
	}

	out << cnt;


	return 0;
}