#include <bits/stdc++.h>

using namespace std;

vector <long long int> prime;
bool isprime[500001];

void eratos(void)
{
	memset(isprime, true, sizeof(isprime));

	for (int j = 2; j <= 500000; j++)
	{
		if (isprime[j])
		{
			prime.push_back(j);
			for (int k = 2 * j; k <= 500000; k += j)
			{
				isprime[k] = false;
			}
		}
	}
}
int main(void)
{
	cin.tie(0);
	ios::sync_with_stdio(false);
	
	eratos();
	long long int n;
	
	cin >> n;

	int res = 0;

	for (int i = 0; i < prime.size(); i++)
	{
		if (prime[i] > n) break;
		long long int val = prime[i] * prime[i];
		if (val - 2 <= n && isprime[val - 2])
		{
			if (val == 4) res++;
			else res += 2;
		}
	}
	
	cout << res << '\n';
	return 0;
}