#include <bits/stdc++.h>
using namespace std;
using ld = long double;
const ld eps = 1e-12;

int main()
{
	ld v;
	while (cin >> v) {
		for (int i = 1;; i++) {
			if (v * v / 19.6 - eps <= 5 * i - 5) {
				cout << i << endl;
				break;
			}
		}
	}
	return 0;
}