#include <stdio.h>
#include <stdlib.h>

const int nmax = int(2e6) + 2;
char p[nmax];

int sieve(int n) {
	int ret = 1;
	for(int i = 3;i*i <= n;i += 2) {
		if(p[i] == 0) {
			for(int j = i + i + i;j <= n;j += i*2) {
				p[j] = 1;
			}
		}
	}

	for(int i = 3;i <= n;i += 2) {
		ret += p[i] ^ 1;
	}
	
	return ret;
}

int main()
{
	freopen("ciur.in","r",stdin);
	freopen("ciur.out","w",stdout);
	int n;
	scanf("%d",&n);
	printf("%d\n",sieve(n));
	return 0;
}