#include<iostream>
using namespace std;

int is_prime(int n){
    int i;
    int flag = 0;
    for(i=2; i<n; i++){
        if(n%i==0) { flag=1; break; }
    }
    return (flag==1)?0:1;
}


int main(){
	int i, j, n, num = 0, count = 0;

	while(cin >> n){
		count = 0;
		for(i = 1; i <= n; i++){
			if(is_prime(i) == 1 && i != 1) count ++;
		}
		cout << count << endl;
	}

	return 0;
}