# -*- coding: utf-8 -*-
=begin
Volume0-0024
=end
require 'bigdecimal'
fh=STDIN
#fh=open("x.txt")

while fh.gets do
  vl = BigDecimal.new($_.chomp)
  y=(vl/9.8)**2*4.9
  yl=((y + 5.0) / 5.0).ceil
  puts yl
end