B19 is downstairs. It takes about 5 min. walking plus staircase or elevator (the escalator goes up!) to get there after passing the security post close to the A3 and the LH lounges. I always use this to go through security, as it usually has shorter lines than the larger control post close to the bars and duty frees (even if you do a little more walking, i.e. ~50 meters, if you have a gate with a number lower than B9).