#include <bits/stdc++.h>
using namespace std;

int main()
{
	int64_t n;
	cin >> n;

	vector<int64_t> ps;
	ps.emplace_back(2);
	for (int64_t i = 3; i <= n; i += 2)
	{
		bool f = true;
		for (auto &p : ps)
		{
			if (i < p * p)
			{
				break;
			}
			f &= i % p != 0;
		}
		if (f)
		{
			ps.emplace_back(i);
		}
	}

	int64_t ans = 0;
	for (auto &x : ps)
	{
		int64_t r = x * x;
		auto itr = lower_bound(ps.begin(), ps.end(), r - 2);
		if (itr != ps.end() && (*itr == r - 2))
		{
			ans++;
		}
	}
	ans *= 2;
	ans--;

	cout << ans << endl;

	return 0;
}