#include<iostream>

int main(){

	double min_v;
	while (std::cin >> min_v){

		double t = min_v / 9.8;
		double sum = 4.9*t*t;

		int y = (sum + 5) / 5;

		std::cout << (5 * y - 5 > sum ? y : y + 1) << std::endl;
	}

	return 0;
}