a = "#"
b = "."
c = ""
while true
  h, w = gets.split(" ").map(&:to_i)
  break if h == 0 && w == 0
  h.times do
    w.times do |i|
      print a if i % 2 == 0
      print b if i % 2 == 1
    end
  puts ""
  c = a
  a = b
  b = a
  end
  pus ""
end