Maximum Sum Subsequence of Fixed Length

Your task is to find the maximum sum of any contiguous subsequence of a specified length \( k \) from a given sequence of integers. If no contiguous subsequence of length \( k \) exists (i.e., if \( k > n \)), output 0.

Given \( n \) (the length of the sequence), \( k \) (the required length of the contiguous subsequence), and the sequence of integers, compute the maximum sum possible from any contiguous subsequence of length \( k \). You are encouraged to use a sliding window approach to solve this problem efficiently.

inputFormat

The input is provided via standard input (stdin) and consists of two lines:

1. The first line contains two space-separated integers \( n \) and \( k \), where \( n \) is the length of the sequence and \( k \) is the desired contiguous subsequence length.
2. The second line contains \( n \) space-separated integers representing the sequence.

outputFormat

Output a single integer representing the maximum sum of any contiguous subsequence of length \( k \). If there is no such subsequence (i.e., when \( k > n \)), output 0.

6 3
1 2 3 -2 5 -1

6