Note that when we say that a character c has k states, that means that there are k different values of c in the input. For instance, if for a given DNA site all the species in the input have either `T' or `C', this site has only 2 states, and not 4. It is clear then, that a k-state character can have no less than k-1 changes.
In the following discussion, we will assume that all characters are binary, i.e., have exactly two possible states, 0 and 1.
