while (ln = gets.chomp) != '0 0'
  h, w = ln.split.map(&:to_i)

  h.times do |i|
    fmt = '#.'
    fmt = '.#' if i % 2 > 0
    s = fmt * (w.to_f / 2).ceil
    s = s[0, s.length-1] if w.to_f % 2 > 0
    puts s
  end

  puts
end