while true do
    h, w = gets.split.map(&:to_i)
    break if h == 0 && w == 0
    for x in 1..h do
        if (x % 2 != 0) then
            for i in 1..w do
                if (i % 2 == 0) then
                    print "."
                else
                    print "#"
                end
            end
        else
            for i in 1..w do
                if (i % 2 != 0) then
                    print "."
                else
                    print "#"
                end
            end
        end
            
        puts ""
    end
    puts ""
end