class Problem
  def exec
    while l = gets do
      i = l.to_i
      res = calc i
      puts res
    end
  end

  def calc(i)
    # ?£????????????????????????????????¨????
    t = i / 9.8

    #?????????????????§??????????????¢????¨????
    y = 4.9 * (t ** 2)

    #??????????????¢????????????????????§???????????°?£???????????????¶????????????????°??????´??°N????±???????
    n = ((y + 5) / 5).ceil
  end
end

p = Problem.new
p.exec