loop do
  a = gets.split.map(&:to_i)
  ans = ""
  break if a[0] == 0 && a[1] == 0
  for i in 0...a[0] do
    for j in 0...a[1] do
      ans << "#" if j % 2 == 1 && i % 2 == 1
      ans << "#" if j % 2 == 0 && i % 2 == 0
      ans << "." if j % 2 == 1 && i % 2 == 0
      ans << "." if j % 2 == 0 && i % 2 == 1
    end
    ans << "\n"
  end
  puts ans
end