#include <cstdio>
#define nmax 2000000

int N;
char a[nmax/16+1];

int main ()
{
	freopen ("ciur.in", "r", stdin);
	freopen ("ciur.out", "w", stdout);

	scanf ("%d", &N);


	int i, nr=1;
	for (i=1; i*(i+1)<=N/2; ++i)
		if (!(a[i/8] & (1<<(i%8))))
		{
			nr++;
			for (int j=2*i+1; j*(2*i+1)<=N; j+=2)
				a[(j*(2*i+1)-1)/2 /8] |= (1<<((j*(2*i+1)-1)/2)%8);
		}

	for (; 2*i+1<=N; ++i)
		if (!(a[i/8] & (1<<(i%8)))) nr++;

	printf ("\n%d\n", nr);
	return 0;
}