inputs = []
loop do
    input = gets.split(" ")
    if input[0] == "0" && input[1] == "0"; break; end
    inputs << input
end

inputs.each do |row_column|
    row_column[0].to_i.times do |i|
        row_column[1].to_i.times do |j|
            if (i + j) % 2 == 0
                print "#"
            else
                print "."
            end
        end
        print "\n"
    end
    print "\n"
end
