
loop{
    a="#"
b="."
h,w=gets.split(" ").map(&:to_i)
break if h==0 and w==0
h.times{|i|
    w.times{|j|
        if (i+j)%2==0
            print("#{a}")
        else
            print("#{b}")
        end
    }
    puts""
}
puts""
}
