Maximum Sum of K Consecutive Elements

You are given an array of n integers and an integer k. Your task is to find the maximum sum of any k consecutive elements in the array.

If k is less than or equal to 0, or if k is greater than n, the result is defined to be 0.

Formally, given an array A with elements \(A_1, A_2, \ldots, A_n\), you need to compute

[ \max_{1 \leq i \leq n-k+1} \sum_{j=i}^{i+k-1} A_j ]

if (n \geq k) and (k > 0); otherwise, output 0.

This is a typical sliding window problem that can be solved in \(O(n)\) time.

inputFormat

The input is read from standard input and consists of two lines:

• The first line contains two space-separated integers: n (the size of the array) and k (the number of consecutive elements to consider).
• The second line contains n space-separated integers representing the elements of the array.

outputFormat

Output a single integer which is the maximum sum of any k consecutive elements in the array. If k is invalid (\(k \le 0\) or \(k > n\)), output 0.

## sample

4 2
100 200 300 400

700

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