lines = readlines.map(&:chomp).map{|line| line.split.map(&:to_i)}
lines.each do |line|
    break if line == [0, 0]
    line[0].times do |i|
        line[1].times do |j|
            if i.odd?&&j.odd? || i.even?&&j.even? then
                print "#"
                next
            end
            if i.odd?&&j.even? || i.even?&&j.odd? then
                print "."
                next
            end
        end
        puts
        end
    puts
end
