## Fill Matrix

Given a `NxN`

matrix. Fill the integers from `1`

to `n*n`

to this matrix that makes the sum of each row, each column and two diagonals equal.

**Example 1:**

```
Input: n = 2
Output: null
Explanation: We need to fill [1, 2, 3, 4] into a 2x2 matrix, which is not possible so return null.
```

**Example 2:**

```
Input: n = 3
Output:
[[8, 3, 4],
[1, 5, 9],
[6, 7, 2]]
Explanation: We need to fill [1, 2, 3 ... 9] into a 3x3 matrix. There is one way to do it
Each row [8, 3, 4] [1, 5, 9] [6, 7, 2] sum is 15.
Each column [8, 1, 6] [3, 5, 7] [4, 9, 2] sum is 15.
The two diagonals [8, 5, 2] [4, 5, 6] sum is 15.
```