One possible scenario is he proved it correct assuming that the ints in the function were mathematical integers(-infinity, ... -1, 0, 1, ..., infinity). In real

One possible scenario is he proved it correct assuming that the ints in the function were mathematical integers(-infinity, ... -1, 0, 1, ..., infinity). In realty all representations of numbers have an upper limit after which the representation will become corrupted or unsupported.