#include "bits/stdc++.h"

using namespace std;

bool isPrime(int x)
{
	for (int i = 2; i*i <= x; i++)
	{
		if (x % i == 0) return false;
	}
	return true;
}

void solve(void)
{
	int n;
	cin >> n;
	int ans = 0;
	for (int i = 2; i * i <= n+2; i++)
	{
		if (isPrime(i) && isPrime(i*i-2))
		{
			if (i == 2) ans++;
			else ans += 2;
		}
	}
	cout << ans << endl;
}

int main()
{
	solve();
	//cout << "yui(*-v・)yui" << endl;
	return 0;
}