#include<iostream>
#include<algorithm>
#include<stdio.h>
#include<string.h>
#include<map>
#include<string>
#include<fstream>
#include<vector>
#include<functional>
using namespace std;
bool isprime(int n) {
	for (int i = 2; i*i <= n; i++) {
		if (n % i == 0)
			return false;
	}
	return true;
}
int main() {
#ifdef LOCAL
	freopen("d:\\datain.txt", "r", stdin);
	freopen("d:\\dataout.txt", "w", stdout);
#endif LOCAL
	int n;
	cin >> n;
	int count = 0;
	for (int i = 5; i <= n; i++) {
		if (isprime(i - 2) && isprime(i))
			count++;
	}
	cout << count;
	return 0;
}