Intuitively, long as primitive type should be faster in case of multiplication or other arithmetic operations than Long as object type. However, my recent submissions to a CF problem 439B - Деву-дурачок disproved this intuition.

15307785 using long, the primitive type got TLE, whilst 15307798 using Long, the object type got Accepted, and has a large timely improvement over the previous one by like 10 times.

Does anyone have any idea why this happened?

Here is another problem :285C - Получаем перестановку