#include <stdio.h>
#include <math.h>
unsigned char V[2000005];
int N;
void citire()
{
	freopen("ciur.in","r",stdin);
   scanf("%d",&N);
}

void ciur()
{
	V[0]=1;
	V[1]=1;
	V[2]=0;
   V[3]=0;
   V[4]=1;
   V[5]=0;
   int m;
   m=sqrt(N);
	for (int i=2;i<=m;++i)
   	{
   	if (V[i]==0)
	   	for (int j=2;j<=m;++j)
         	V[i*j]=1;
      }
}
void afisare()
{
	freopen("ciur.out","w",stdout);
	long int s=0,i;
	for (i=0;i<N;++i)
   	if (V[i]==0)
      	s++;
   printf("%ld\n",s);
}
int main()
{
	citire();
   ciur();
   afisare();
   return 0;
}