I think this problem is not very hard and it's interesting.

Description:

You are given $$$2$$$ arrays $$$a$$$ and $$$b$$$ and the length of them is $$$n$$$.

- $$$1$$$, $$$3$$$, $$$5$$$, ......, $$$2 * n - 1$$$ is in $$$a$$$.

- $$$2$$$, $$$4$$$, $$$6$$$, ......, $$$2 * n$$$ is in $$$b$$$.