#include <cstdio>
#include <iostream>
using namespace std;

int main()
{	
	unsigned long int N,i,j;
	unsigned int contor=0;
	bool ok;
	FILE *intrare,*iesire;
	intrare=fopen("ciur.in","r");
	fscanf(intrare,"%ld" ,&N);
	fclose(intrare);
	for(i=2;i<=N;i++)
	{	
		ok=true;
		for(j=2;j<=i/2;j++)
		{
			if(i%j==0) ok=false;
		}
		if(ok==false) contor=contor+1;
	}
	iesire=fopen("ciur.out","w");
	fprintf(iesire,"%d",contor-1);
	fclose(iesire);
	return 0;
}