#include <stdio.h>
#include <stdlib.h>
#include<math.h>
int prim(int m){
    int i;
    for(i=2;i<=sqrt(m);i++)
       if(m%i==0)
        return 1;
       return 0;

}

int main()
{
    FILE * in,* out;
    in=fopen("ciur.in","r");
    out=fopen("ciur.out","w");
       int n,i,k=0;
    fscanf(in,"%d",&n);
    if(n>2){
     for(i=2;i<=n;i++)
       if(prim(i)==0)
        k++;
       fprintf(out,"%d",k);
    }
    if(n==2)
   fprintf(out,"%d",1);
   if(n==1)
     fprintf(out,"%d",1);

    return 0;
}