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

int main()
{
    int N, x=3, nr=1, d,cnt=0;
    FILE *r,*w;
    r=fopen("ciur.in","r");
    w=fopen("ciur.out","w");

    fscanf(r,"%d", &N);
    while(x<=N){
        nr=1;
        d=2;
        while(d<x){
            if(x%2==0){
                nr=0;
                d=x;
            }
            d++;
        }
        x++;
        if(nr){
            cnt++;
        }
    }
    fprintf(w,"%d",cnt);
}