input: from typing import List
  
  def merge_sort(A: List[int], B: List[int]) -> List[int]:
      """
      Merge two sorted lists A and B into a single sorted list.
      Compare the first elements of both lists and add the smaller one to the result list.
      Move the pointer of the list from which the element was taken to the next element.
      Continue this process until either list is exhausted. Add the remaining elements of
      both lists to the result list.
      
      >>> merge_sort([3, 6, 8, 10, 11], [2, 5, 7, 12])
      [2, 3, 5, 6, 7, 8, 10, 11, 12]
      """
output:     result = []
      i, j = 0, 0
      while i < len(A) and j < len(B):
          if A[i] < B[j]:
              result.append(A[i])
              i += 1
          else:
              result.append(B[j])
              j += 1
      result.extend(A[i:])
      result.extend(B[j:])
      return result