#include<iostream>
using namespace std;

#define floor(x) (x*5-5)

double t;

int   main()
{
	while (cin >> t)
	{
		double s;
		s = t * t / (2 * 9.8);
		
		s=(s + 5) / 5;
		s += 0.9;
		cout << int(s) << endl;
	}
	return 0;
}
