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