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# Problem DPeningar

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Image from flickr.com

Tómas has found himself in a strange world. This world consists of $n$ cells arranged in a circle. Thus cells $i$ and $i+1$ are adjacent for $1 \leq i < n$, and cells $1$ and $N$ are also adjacent. In each cell there is an $a_ i$ amount of money. Tómas starts at cell $1$. In each step he moves $d$ cells. When landing in a cell Tómas takes all the money in that cell. Can you find out how much money Tómas will get if he continues walking forward until he can’t gather any more money?

## Input

The first line of the input contains two integers $n,d$ ($1 \leq n \leq 10^5$, $1 \leq d \leq 10^{14}$), where $n$ is the number of cells and $d$ is how many cells Tómas moves forward with each step.

The next line contains $n$ integers, $a_ i$ ($1 \leq a_ i \leq 10^9$), denoting how much money is in the $i$-th cell.

## Output

Print a single integer, how much money Tómas will end up with.

## Scoring

 Group Points Constraints 1 25 $1 \leq n, a_ i \leq 100$, $d = 1$ 2 25 $1 \leq n, d, a_ i \leq 100$ 3 50 No further constraints
Sample Input 1 Sample Output 1
4 1
1 1 1 1

4

Sample Input 2 Sample Output 2
4 2
1 5 3 5

4

Sample Input 3 Sample Output 3
5 3
1 2 3 4 5

15

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