Given an integer array `nums` of length `n`, you want to create an array `ans` of length `2n` where `ans[i] == nums[i]` and `ans[i + n] == nums[i]` for `0 <= i < n` (0-indexed).

Specifically, `ans` is the concatenation of two `nums` arrays.

Return the array `ans`.

Example 1:

    Input: nums = [1,2,1]
    Output: [1,2,1,1,2,1]
    Explanation: The array ans is formed as follows:
    - ans = [nums[0],nums[1],nums[2],nums[0],nums[1],nums[2]]
    - ans = [1,2,1,1,2,1]

Example 2:

    Input: nums = [1,3,2,1]
    Output: [1,3,2,1,1,3,2,1]
    Explanation: The array ans is formed as follows:
    - ans = [nums[0],nums[1],nums[2],nums[3],nums[0],nums[1],nums[2],nums[3]]
    - ans = [1,3,2,1,1,3,2,1]

Constraints:

- `n == nums.length`
- `1 <= n <= 1000`
- `1 <= nums[i] <= 1000`