#include <stdio.h>
#include <stdlib.h>
#include<math.h>
int prim(int m){
    int i;
    for(i=2;i<=sqrt(m);i+=2)
       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);
     for(i=3;i<=n;i=i+2)
       if(prim(i)==0)
        k++;
       fprintf(out,"%d",k);
    return 0;
}