#include <iostream>
#include <cmath>
#include <vector>

int main()
{
	double velocity = 0;
	while (std::cin >> velocity) {
		double time = velocity / 9.8;
		double y = 4.9 * time * time;
		int floor = static_cast<int>(y / 5.0) + 2;
		std::cout << floor << std::endl;
	}

	return 0;
}