distance takes two const int * parameters and returns how far apart the two values are – always
nonnegative, regardless of which one is larger.
The ternary operator from Module 1 fits this exactly: (*a > *b) ? (*a - *b) : (*b - *a) subtracts the smaller
from the larger either way, so the result can never come out negative. Both parameters are const for the same
reason as the previous exercise – this function reads two values and produces a new one; it never needs to write
through either pointer.