while true
  h, w = gets.chomp.split.map { |e| e.to_i }
if h%2 == 0
  (h/2).times {
  if w%2 == 0
      puts "#{"#."*(w/2)}\n#{".#"*(w/2)}"
  else
      puts "#{"#."*(w/2)}#\n#{".#"*(w/2)}."
    end }
else
  (h/2).times {
    if w%2 == 0
     puts "#{"#."*(w/2)}\n#{".#"*(w/2)}"
    else
     puts "#{"#."*(w/2)}#\n#{".#"*(w/2)}."
      end }
    end
    if w%2 == 0
     puts "#{"#."*(w/2)}"
     else
     puts "#{"#."*(w/2)}#"
    end
    puts ""
if h == 0 and w == 0
      break
    end
end