if __FILE__ == $0
  while line = gets
    min_speed = line.to_f
    t = min_speed / 9.8
    min_height = 4.9 * t**2
    n = 1
    while true
      if n * 5 - 5 >= min_height
        break
      end
      n += 1
    end
    puts n
  end
end