ArraySliding Window
Find the largest sum of any contiguous subarray that has exactly k elements.
Input
Line 1: n and k. Line 2: n integers.
Output
Print the maximum sum of a subarray of length k.
Constraints
1 <= k <= n <= 10^5 -10^4 <= each value <= 10^4
Example 1
Input
6 3 2 1 5 1 3 2
Output
9
The window 5 1 3 sums to 9, the largest of any three in a row.