#include <iostream>
#include <cmath>
using namespace std;


int main()
{
	double s;
	while (cin >> s){
		for (int i = 1;; i++){
			double h = 5 * i - 5;
			double v = sqrt(2 * 9.8 * h);
			if (v >= s){
				cout << i << endl;
				break;
			}
		}
	}
	return 0;
}