#include <iostream>
#include <cstdint>
#include <vector>

using namespace std;

int main()
{
	cin.tie(nullptr);
	ios::sync_with_stdio(false);

	uint64_t N;
	cin >> N;

	uint32_t l = 0, r = 1'000'000'001;
	while (l + 1 < r)
	{
		const auto c = (l + r) >> 1;
		if (static_cast<uint64_t>(c) * c <= N) l = c;
		else r = c;
	}

	cout << l << '\n';
	return 0;
}