#include <fstream>

using namespace std;

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

bool c[1000000 + 5];
int n, nr, i;

void ciur()
{
	int i, j;
	for (i = 3; i * i <= n; i += 2)
		if (!c[i / 2])
			for (j = i * i; j <= n; j += 2 * i)
				c[j / 2] = 1;
}

int main()
{
	fin >> n;
	ciur();
	for (i = 3; i <= n; i += 2)
		if (!c[i / 2])
			++nr;
	fout << nr + 1;
	fin.close();
	fout.close();
	return 0;
}