input: Write a function to merge two sorted lists, A and B, into a single sorted list. The function should compare the first element of A with the first element of B. If the element from A is greater than the element from B, the element from B should be added to the result list and the pointer of B should move to the next element. If the element from A is smaller, the pointer of A should move to the next element. If one list is exhausted, the remaining elements of the other list should be 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([], [1, 2, 3])==[1, 2, 3]
  assert merge_sort([1, 2, 3], [])==[1, 2, 3]
  assert merge_sort([], [])==[]
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
  