#include <iostream>
using namespace std;

int main(void)
{
	double v, times, hight, street;

	while (cin >> v) {
		times = v / 9.8;
		hight = 4.9 * times * times;
		street = (hight + 5.0) / 5.0;
		printf("%.0f\n", street);
	}
	
	return 0;
}