def aux(v)
  t = v / 9.8
  y = 4.9*t**2
  (1..1000).each {|n|
    if 5*n-5>=y
      return n
    end
  }
  1/0
end

def main
  fh=STDIN
  #fh=File.new("x.txt", "r")
  while fh.gets
    v = $_.chomp.to_f
    puts aux(v)
  end

end

if $0 == __FILE__ then
  main
end
