class Problem
  def exec
    while l = gets do
      f = l.to_f
      res = calc f
      puts res
    end
  end

  def calc(f)
    t = f / 9.8
    y = 4.9 * (t ** 2)
    ((y + 5) / 5).ceil
  end
end

p = Problem.new
p.exec