#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <cctype>
#include <string>
#include <algorithm>
#include <vector>
#include <queue>
#include <deque>
#include <set>
#include <stack>
#include <cassert>
using namespace std;

#define PRO "ciur"
void OpenFiles(int EVAL)
{
	if(EVAL)
	{
		char input[100] = PRO, output[100] = PRO;
		freopen(strcat(input, ".in"),"r",stdin);
		freopen(strcat(output,".out"),"w",stdout);
	} else
	{
		freopen("test.in","r",stdin);
		freopen("test.out","w",stdout);
	}
}

#define MAX 2000001
#define INF 0xffffff

unsigned char p[MAX/8];
int n,nr;

void Ciur()
{
	int i=2;
	while(i<=1414)
	{
		while(p[i/8]&(1<<(i%8)))i++;
		for(int j=i*i;j<MAX;j+=i)p[j/8]|=1<<(j%8);
		i++;
	}
	for(int i=2;i<=n;i++)
		if(p[i/8]&(1<<(i%8))) ;else nr++;
}

int main(int argv,char *args[])
{
	OpenFiles(argv==0);	
	// start
		scanf("%d",&n);
		Ciur();
		printf("%d\n",nr);
	return 0;
}