There is a pizza with `3n` slices of varying size, you and your friends will take slices of pizza as follows:

- You will pick any pizza slice.
- Your friend Alice will pick the next slice in the anti-clockwise direction of your pick.
- Your friend Bob will pick the next slice in the clockwise direction of your pick.
- Repeat until there are no more slices of pizzas.

Given an integer array `slices` that represent the sizes of the pizza slices in a clockwise direction, return the maximum possible sum of slice sizes that you can pick.

Example 1:

    Input: slices = [1,2,3,4,5,6]
    Output: 10
    Explanation: Pick pizza slice of size 4, Alice and Bob will pick slices with size 3 and 5 respectively. Then Pick slices with size 6, finally Alice and Bob will pick slice of size 2 and 1 respectively. Total = 4 + 6.

Example 2:

    Input: slices = [8,9,8,6,1,1]
    Output: 16
    Explanation: Pick pizza slice of size 8 in each turn. If you pick slice with size 9 your partners will pick slices of size 8.

Constraints:

- `3 * n == slices.length`
- `1 <= slices.length <= 500`
- `1 <= slices[i] <= 1000`