If you know your powers of two 1, 2, 4, 8, 16, 32, 64, 128, 256, 512 conversion from miles to kilometers is just two steps lexicographically 1, 128, 16,

If you know your powers of two 1, 2, 4, 8, 16, 32, 64, 128, 256, 512 conversion from miles to kilometers is just two steps lexicographically 1, 128, 16, 2, 256, 32, 4, 512, 64, 8 Ex.: 32 miles is 51.2 kilometers 80 miles is 128 kilometers (wrap around!) See https://news.ycombinator.com/item?id=20546927 https://news.ycombinator.com/item?id=20546927