#include <stdio.h>
#include <math.h>
long i, j, n, k=0;
int main()
{
 FILE *f=fopen("ciur.in", "r");
 fscanf(f, "%ld", &n);
 fclose(f);

 if(n>=2) k=1;
 for(i=3;i<=n;i+=2)
  {
   j=3;
   while((j<=sqrt(i))&&(i%j!=0)) j+=2;
   if(i%j!=0) k++;
  }
 f=fopen("ciur.out", "w");
 fprintf(f, "%ld", k+1);
 fclose(f);
 return 0;
}