I'm sorry, the backslashes disappeared from my post, too!
They were there in the preview!!

So, instead, I shall use the ??/ Trigraph Sequence - which is equivalent to a backslash and intended for just this situation.

Wherever you see "??/" visualise just a single backslash:

#define MAX(A,B)                ??/
  if( A > B )                   ??/
      return A; // A is biggest ??/
  else                          ??/
      return B; // B is biggest

Will expand as:

if( A > B ) return A; // A is biggest else  return B; // B is biggest 
           ^                         ^    ^
           |                         |    |
           +-------------------------+----+---- Backslashes & newlines removed

Which, as I said, will obviously not compile!