Maximum Sum Subarray of Fixed Length

You are given an array of n integers and a positive integer w. Your task is to find the maximum sum of any contiguous subarray of length exactly w.

In other words, if the array is denoted by \(a_1, a_2, \dots, a_n\), you need to determine the maximum possible value of \[ S = a_i + a_{i+1} + \cdots + a_{i+w-1} \] for any valid index \(i\) such that \(1 \le i \le n-w+1\).

If w is greater than n, your program should output the error message "Window size w must be less than or equal to the length of the list".

inputFormat

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

• The first line contains two integers n and w, where n is the number of elements in the array, and w is the fixed subarray length.
• The second line contains n integers separated by spaces representing the elements of the array.

You may assume that all integers are within a reasonable range to avoid overflow issues.

outputFormat

If w is less than or equal to n, print a single integer on stdout---the maximum sum of any contiguous subarray of length w.

If w > n, print the following error message exactly as shown:

Window size w must be less than or equal to the length of the list

## sample

6 2
1 2 3 4 5 6

11

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