In the decimal system (base 10), a natural number is represented
as a sequence dndn−1 . . . d0 of (decimal) digits, each of which is
in the range 0..9. The value of the number is d0 ×100 +d1 ×101
+···+ dn ×10n. Similarly, in the binary system (base 2), a natural
number is represented as a sequence bnbn−1 · · · b0 of (binary)
digits, each of which is 0 or 1. The value of the number is b0...