# include <algorithm>
# include <cstdio>

using namespace std;

int n,k=1;
char p[100000000/2/8+1];

int main()
{
	freopen("ciur.in","r",stdin);
	freopen("ciur.out","w",stdout);
	scanf("%d", &n);

    for (int i = 1; ((i * i) << 1) + (i << 1) <= n; i += 1)     
		if ((p[i >> 3] & (1 << (i & 7))) == 0) 
			for (int j = ((i * i) << 1) + (i << 1); (j << 1) + 1 <= n; j += (i << 1) + 1) 
				p[j >> 3] |= (1 << (j & 7));
	for (int i = 1; 2 * i + 1 <= n; ++i)  
		if ((p[i >> 3] & (1 << (i & 7))) == 0) 
			k++;

	printf("%d", k);
	return 0;
}