Complete increment so it adds 1 to the int its reference parameter refers to. main reads n, calls
increment(n) (note: no &n at the call site – that’s the other giveaway this is a reference, not a pointer),
and prints the result.
This is the exact double_value-style out-parameter pattern from Module 2, rewritten with a reference instead of a
pointer – same effect on the caller’s variable, no dereferencing required to get there.