No, but return value is integer anyway, so there is no possible way to return correct value using integer. We can return 0 in this case, because input data will be kind of incorrect, but I don't think it's a good way to solve the task.

Description says: "Input will always be a non-negative integer.", so we can omit handling this case

What about negative values? For example n = -5, m = -4. I think it should return 0. Your solution will give 19.