while true
    rect = gets.split.map(&:to_i)
    break if (rect[0] == 0 && rect[1] == 0)
    tate = rect[0]/2
    yoko = rect[1]/2
    
    if rect[0] % 2 == 0 && rect[1] % 2 == 0 then
        tate.times do
            puts '#.'*yoko
            puts '.#'*yoko
        end
    end

    if rect[0] % 2 == 1 && rect[1] % 2 == 0 then
        tate.times do
            puts '#.'*yoko
            puts '.#'*yoko
        end
        puts '#.'*yoko
    end
    
    if rect[0] % 2 == 0 && rect[1] % 2 == 1 then
        tate.times do
            print '#.'*yoko
            puts "#"
            print '.#'*yoko
            puts "."
        end
    end
    
    if rect[0] % 2 == 1 && rect[1] % 2 == 1 then
        tate.times do
            print '#.'*yoko
            puts "#"
            print '.#'*yoko
            puts "."
        end
        print '#.'*yoko
        puts "#"
    end
    
    puts
    
end