loop {
  h, w = gets.split(" ").map(&:to_i)
  if h == 0 && w == 0
        break
    end
    for n in 1..h
        if n%2 == 1
            for n in 1..h
                i = 0
                while i < (w-1)
                    print "#"
                    i += 1
                    print "."
                    i += 1
                end
                if w%2 == 1
                    puts "#"
                end
                i = 0
            end
            puts "\n"
        else
            for n in 1..h
                i = 0
                while i < (w-1)
                    print "."
                    i += 1
                    print "#"
                    i += 1
                end
                if w%2 == 1
                    puts "."
                end
                i = 0
            end
            puts "\n"
        end
    end
    puts "\n"
}