/*
    Keep It Simple!
*/

#include<stdio.h>

int nrp,n;
bool prime[2000005];

int main()
{
   freopen("ciur.in","r",stdin);
   freopen("ciur.out","w",stdout);

   scanf("%d",&n);

   for(int i=3;i<=n;i+=2)
   {
      if( !prime[i] )
      {
          nrp++;
          for(int j=i;j<=n;j+=i)
             prime[j] = 1;
      }
   }

   printf("%d",nrp+1);
}