while input = gets
    h, w = input.chomp.split(" ").map(&:to_i)
    
    if h == 0 && w == 0
        exit
    end
    
    for i in 1..h
        for j in 1..w
            if i % 2 != 0
                if j % 2 != 0
                    print "#"
                else
                    print "."
                end
            else
                if j % 2 != 0
                    print "."
                else
                    print "#"
                end
            end
        end
        puts ""
    end
    puts ""
end
