#include <bits/stdc++.h>

int main()
{
	int N;
	scanf("%d", &N);
	std::vector<bool> isPrime(N + 1, true);
	std::vector<int64_t> primeList;
	isPrime[0] = isPrime[1] = false;
	for (int64_t i{2}; i <= N; i++)
	{
		if (!isPrime[i]) continue;
		primeList.push_back(i);
		for (int64_t j{2 * i}; j <= N; j += i)
			isPrime[j] = false;
	}
	int64_t count{};
	for (int p_i{}; p_i < (int)primeList.size(); p_i++)
		for (int r_i{}; r_i < (int)primeList.size(); r_i++)
		{
			int64_t q{primeList[r_i] * primeList[r_i] - primeList[p_i]};
			if (2 <= q && q <= N && isPrime[q])
				count++;
		}
	printf("%lld\n", count);

	return 0;
}