Please subscribe to the official Codeforces channel in Telegram via the link: https://t.me/codeforces_official.
×

Virtual contest is a way to take part in past contest, as close as possible to participation on time. It is supported only ACM-ICPC mode for virtual contests.
If you've seen these problems, a virtual contest is not for you - solve these problems in the archive.
If you just want to solve some problem from a contest, a virtual contest is not for you - solve this problem in the archive.
Never use someone else's code, read the tutorials or communicate with other person during a virtual contest.

No tag edit access

D. Single-use Stones

time limit per test

1 secondmemory limit per test

256 megabytesinput

standard inputoutput

standard outputA lot of frogs want to cross a river. A river is $$$w$$$ units width, but frogs can only jump $$$l$$$ units long, where $$$l < w$$$. Frogs can also jump on lengths shorter than $$$l$$$. but can't jump longer. Hopefully, there are some stones in the river to help them.

The stones are located at integer distances from the banks. There are $$$a_i$$$ stones at the distance of $$$i$$$ units from the bank the frogs are currently at. Each stone can only be used once by one frog, after that it drowns in the water.

What is the maximum number of frogs that can cross the river, given that then can only jump on the stones?

Input

The first line contains two integers $$$w$$$ and $$$l$$$ ($$$1 \le l < w \le 10^5$$$) — the width of the river and the maximum length of a frog's jump.

The second line contains $$$w - 1$$$ integers $$$a_1, a_2, \ldots, a_{w-1}$$$ ($$$0 \le a_i \le 10^4$$$), where $$$a_i$$$ is the number of stones at the distance $$$i$$$ from the bank the frogs are currently at.

Output

Print a single integer — the maximum number of frogs that can cross the river.

Examples

Input

10 5

0 0 1 0 2 0 0 1 0

Output

3

Input

10 3

1 1 1 1 2 1 1 1 1

Output

3

Note

In the first sample two frogs can use the different stones at the distance $$$5$$$, and one frog can use the stones at the distances $$$3$$$ and then $$$8$$$.

In the second sample although there are two stones at the distance $$$5$$$, that does not help. The three paths are: $$$0 \to 3 \to 6 \to 9 \to 10$$$, $$$0 \to 2 \to 5 \to 8 \to 10$$$, $$$0 \to 1 \to 4 \to 7 \to 10$$$.

Codeforces (c) Copyright 2010-2018 Mike Mirzayanov

The only programming contests Web 2.0 platform

Server time: Dec/09/2018 23:46:43 (d1).

Desktop version, switch to mobile version.

Supported by

User lists

Name |
---|