#include<iostream>
#include<string>
#include <stdio.h>
#include <math.h>
using namespace std;
int main(){
	int n;
	while(cin>>n){
		int count=0;
		for(int i=2;i<=n;i++){
			int j=2;
			while(true){
				if(i%j==0)
					break;
				if(j>(int)sqrt((double)i)){
					count++;
					break;
				}
				j++;
			}
		}
		cout<<count+1<<endl;
	}
	return 0;
}