Captain Akeno and the crew stopped at a floating mall to replenish the ship's supply of toilet paper. As any normal girl does, the captain stopped at a shoe store, where they had two awesome deals. The deals are as follows:

- If you group two pairs of shoes, you get the cheaper one at a
.*50% DISCOUNT* - If you group three pairs of shoes, you get the cheapest one for
.*FREE*

Captain Akeno had already placed the pairs of shoes on the conveyor when she was told that she can only group adjacent pairs. The group of girls didn't have much money at hand, so they kindly ask you to tell them the minimum obtainable price.

#### Input Specification

The first line of input will contain the integer (), the number of pairs of shoes.

The second line of input will contain space-separated integers representing the prices of the pairs of shoes.

#### Output Specification

On the first line, you must print the smallest obtainable price with one decimal.

#### Sample Input

```
5
100 27 15 25 400
```

#### Sample Output

`538.5`

## Comments

Are we limited to one deal for the entire transaction or can we choose both deals in various quantitues for the transaction?

We assume they can get one of each deal right? And they don't affect each other?

Should the price round to one decimal, or just express one decimal? Ex: Does 45.78 become 45.7 or 45.8?

It should be rounded. 45.78 becomes 45.8

Alright, but what if there is no decimal? Ex if the answer is 178, will it mark it as wrong if I output 178.0?

It will mark 178 wrong I think. You should always have a decimal.

Can you only do any grouping operation once?

which is the bigger price that a shoe can have?

The maximum price of a pair of shoes is 10000.