In a coding method, a (2N-1)st original block of m bits is encoded
as an A type weighted block of n bits and a 2Nth original block of m
bits is encoded as a B type weighted block of n bits. In a decoding method, if
a weighted block of n bits is the A type block, the weighted block of n bits is
decoded as the (2N-1)st original block of m bits, and if otherwise,
the weighted block of n bits is decoded as the 2Nth original block of
m bits.
