#include <iostream>
#include <stdio.h>
#include <string.h>
#include <math.h>
#include <algorithm>
#include <stdlib.h>

using namespace std;


int main(){

	int i, j, k;
	int n;

	while(cin >> n){

		int count = 0;

		if(n>2){
			count ++;
			for(i=3 ; i<=n ; i+=2){
				for(j=3 ; j<=i ; j+=2){
					k = i % j;
					if(k == 0) break;
				}
				if(j == i) count ++;
			}
		}
		cout << count << endl;

	}


	return 0;
}