export function maxWindowSum(numbers: number[], k: number): number {
  if (numbers.length < k) return -1

  let windowSum = 0

  // First window sum
  for (let i = 0; i < k; i++) {
    windowSum += numbers[i]
  }

  let maxSum = windowSum

  // Update window sum and replace maxSum if needed
  for (let i = k; i < numbers.length; i++) {
    windowSum -= numbers[i - k]
    windowSum += numbers[i]

    if (windowSum > maxSum) maxSum = windowSum
  }
  
  return maxSum;
}