There is an array of integers given. You have to return the largest sum of non-adjacent numbers.

Write a function `solve`

that have the following parameter(s):

1.) *arr = an array of integer*

**Example**

Input:

`[2, 4, 6, 8]`

Output:

The function will return,

`12`

**Explanation**

The sum of two non-adjacent numbers `4`

and `8`

from an array [2, 4, 6, 8] will be `12`

.

**Constraints**

• Number of the elements in the array will be greater than or equal to 1 and less than or equal to 800.

• Each element in an array will be 0 or negative or less than 1000.