input: Write a function to merge two large lists A and B such that the resulting list is sorted in non-decreasing order. The function should compare the first elements of both lists and add the smaller one to the result list. If the element from list A is smaller, move to the next element of A; if the element from list B is smaller, move to the next element of B. Continue this process until all elements from both lists are added to the result list.
  def merge_sort(A, B):
   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 += A[i:]
   result += B[j:]
  
   return result
  
  assert merge_sort([3, 6, 8, 10, 11], [2, 5, 7, 12]) == [2, 3, 5, 6, 7, 8, 10, 11, 12]
  assert merge_sort([1, 3, 5], [2, 4, 6]) == [1, 2, 3, 4, 5, 6]
  assert merge_sort([10, 20, 30], [9, 11, 25]) == [9, 10, 11, 20, 25, 30]
  assert merge_sort([], [1, 2, 3]) == [1, 2, 3]
  assert merge_sort([1, 2, 3], []) == [1, 2, 3]
output: def merge_sort(A, B):
   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 += A[i:]
   result += B[j:]
  
   return result