while str = STDIN.gets
  n = str.split(" ")
  a = n[0].to_i
  b = n[1].to_i

  if a == 0 && b == 0
    break
  else
    for h in 0..a-1 do
      for w in 0..b-1 do
        if h % 2 == 0 && w % 2 == 0
          print "#"
        elsif h % 2 == 0 && w % 2 != 0
          print "."
        elsif h % 2 != 0 && w % 2 == 0
          print "."
        else
          print "#"
        end
      end
       print "\n"
  end
  print "\n"
  end
end

