#include<iostream>
using namespace std;

typedef double dbl;

int main() {
	dbl v, t, y;
	while (cin >> v) {
		t = v / 9.8;
		y = 4.9 * t * t;
		int N = 1;
		while (5 * N - 5 < y) {
			N++;
			if (5 * N - 5 >= y) {
				cout << N << endl;
				break;
			}
		}
	}
}
