while 1 do
  h,w=gets.split.map(&:to_i)
  if h==0 and w==0 then
    break
  end
  for i in 1..h
    str=''
    for j in 1..w
      if (i+j)%2>0 then
        str+='.'
      else
        str+='#'
      end
    end
    puts str
  end
  puts ''
end  

