loop do
    h, w = gets.split.map(&:to_i)

    if h == 0 && w == 0
        break
    end

    odd = (".#" * w)[0..(w-1)]
    even = ("#." * w)[0..(w-1)]

    for i in 0..h-1
        if i % 2 == 0
            puts even
        else
            puts odd
        end
    end
        
    puts
end