SP18102 QTGIFT1 - New year love story

With brother's help, DB has successed in flirt with TN. (see QTNOEL). But now he has another problem : In Vietnamese Tet holidays (Vietnam's Lunar New Year), there is a custom called 'Li xi' that adult give children money in red packs, to wish them strong and happy. DB's family has a very special method to give children Li xi : There are $n$ Li xi packs, every pack has $a[i]$ VND – Vietnamese unit of money, and a random positive integer $k (1 ≤ k ≤ n)$. DB can take any pack, but mustn't take $k$ packs in a row. Let's help him to find the way to take the maximum of money.

First line : two integers $n$ and $k$ Second line : $n$ integers, the $i$-th number is $a[i]$.

A single number $s$ – the maximum money DB can take.

- $0 ≤ a[i] ≤ 2000$ - $n ≤ 10^6$