A sensor logs one integer energy reading per second. Given a fixed window length k, you want to find the single window of k consecutive readings whose total energy is the largest.

Return that maximum total. Readings may be negative (energy can be drained).

Input format

Line 1: two integers n and k separated by a space, where n is the number of readings and k is the window length. Line 2: n space-separated integers, the readings in order.

Output format

A single integer: the maximum sum over all contiguous windows of exactly k readings.

Constraints

• 1 ≤ k ≤ n ≤ 100000
• -1000000 ≤ each reading ≤ 1000000
• There is always at least one valid window (since k ≤ n).

6 3
2 1 5 1 3 2

9

5 2
-4 -2 -7 -1 -3

-4