48. Maximum Sum Subarray of Size K

Difficulty: easy · Array, Prefix Sum

Problem

Given an array of `n` integers and an integer `k`, find the maximum sum of any contiguous subarray of exactly `k` elements.

Input

- Line 1: two integers `n` and `k`. - Line 2: `n` space-separated integers.

Output

Print the maximum sum of a window of size `k`.

Example 1

Input:
6 3
2 1 5 1 3 2
Output:
9

Explanation: The window 5 1 3 has sum 9, the largest of the four windows (8, 7, 9, 6).

Example 2

Input:
4 2
-1 -2 -3 -4
Output:
-3

Explanation: All windows are negative; -1 + -2 = -3 is the largest.

Constraints

- 1 <= k <= n <= 10^5 - -10^9 <= arr[i] <= 10^9

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