Hello, I run into the same error, numbers[0] and numbers[1] are int values an explicit cast like "result+= (long)numbers[0] should solve the problem. Without explicit cast there is an overflow. Hope it helps you.

Update: I was wrong, the tester works. After working on a similar problem, I finally understood what was happening and modified my code accordingly. It now works will all the tests and I finally got credit.

Thank you to Unnamed and Chrono79 for your patience and understanding ( and the gentle hints that you gave).

All I will say here is that in the C++ version, you have to really understand your data types.
Solution will be posted in the next reply (as Spoiler).

just to be sure... x)

The sum of ints is an int.
C++17, paragraphs 8.5.6, 8.3 and 7.6: http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2017/n4713.pdf

There are no restrictions, so it's any pair of numbers.