#include <stdio.h>
#include <stdlib.h>

int main()
{
   int w, r;
   FILE* a, *b;
         a = fopen("ciur.in", "r");
         b = fopen("ciur.out", "w");

         fscanf(r, "%d", &w);
         int i, n, is_prim, cnt=0;
          i=2;


        while(i<=n) {
            is_prim=1;
            int d;
            d=2;
            while(d<i) {
                if(i%d==0){
                    is_prim=0;
                    d=i;

                }
            d++;
            }
       if(is_prim){
        cnt=cnt+1;
       }
       i++;
        }
        fprintf(w, "%d", cnt);
}