#include<iostream>
using namespace std;
int main() {
	double v;
	while (cin >> v){
		double y = (v / 9.8)*(v / 9.8) * 4.9;
		y -= 5;
		int n = 0;
		while (true){
			if (5 * n >= y){
				cout << n << endl;
				goto grav;
			}
			else n++;
		}
	grav:;
	}
}