loop do
  a,b = gets.split().map(&:to_i)
  break if a == 0 && b == 0
  a.times do |c|
    if c == 0 || c % 2 == 0
      b.times do |d|
        if d == 0 || d % 2 == 0
          print "#"
        else
          print "."
        end
      end
    else
      b.times do |e|
        if e == 0 || e % 2 == 0
          print "."
        else
          print "#"
        end
      end
    end
  print "\n"
  end
  puts ""
end
