#include <iostream>

using namespace std;

int main() {
	double v;

	while (cin >> v) {
		v = 4.9 * ((v / 9.8) * (v / 9.8));

		for (int i = 1; ; i++) {
			if (5 * i - 5 > v) {
				cout << i << endl;
				break;
			}
		}
	}
	return 0;
}