#include <iostream>
using namespace std;

int main()
{
	double v, t, y;
	int N;

	while (cin >> v)
	{
		if (cin.eof()) break;

		t = v / 9.8;
		N = (int)((4.9 * t * t + 5) / 5 + 0.9);
		cout << N << endl;
	}
	return 0;
}