#include<iostream>
#include<cmath>
using namespace std;

int main() {
	double x;
	while (cin >> x) {
		double v = 0, t, y;
		for (int i = 1;; i++) {
			y = 5 * i - 5;
			t = sqrt(y / 4.9);
			v = 9.8*t;
			if (v >= x) {
				cout << i << endl;
				break;
			}
		}
	}
}
