#include <bits/stdc++.h>
#define PI 3.14159265359
using namespace std;

int main() {
	double v, y, t;
	while (cin >> v) {
		t = v / 9.8;
		y = 4.9 * t * t;

		int N = 1;
		while (1) {
			int height = 5 * N - 5;
			if (height >= y) {
				break;
			}
			else {
				N++;
			}
		}

		cout << N << endl;
	}
}
