#include <iostream>
using namespace std;

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