Or one in Ab minor with seven flats which makes you realise how they got named 'accidentals'. I was about to explain the 'rule of 7' on how to get from 4 flats BEAD to 3 #s CGF without resorting to manuscript paper when I realised it had got mixed up with a list of Thame cab numbers in the back of a notebook (and anyway what you really need to know is how to get to the relative minot and it's really amazing how few people realise that all you need to do is subtract 3 backwards) but if/when you really have occasion to get from A flat to A major you subtract the 4 flats from 7 and end up with 3 #s. And so on.