Update pizza-with-3n-slices.cpp

Author: kamyu104

C++/pizza-with-3n-slices.cpp

@@ -4,6 +4,7 @@
 // [observation]
 // 1. we can never take two adjacent slices.
 // 2. if we want some set of N / 3 non-adjacent slices, there is always a way to take
+//
 // [proof]
 // - for N = 3, it is obviously true.
 // - for N' = N + 3,