#include <iostream>
using namespace std;

int main() {
	double v;
	
	while (cin >> v) {
		double t = v / 9.8;
		double y = 4.9 * t * t;
		int kai = (y + 5 - 1e-11) / 5;
		kai++;
		cout << kai << endl;
	}
	return 0;
}