from typing import List


def combine_lists(list_a: List[int], list_b: List[int]) -> List[int]:
    """
    Combines 2 integer lists
    :param list_a: List a
    :param list_b: List b
    :return merged list of a & b
    """
    list_a_index = 0
    list_b_index = 0
    merged_list = []

    # both lists have some items left in them
    while list_a_index < len(list_a) and list_b_index < len(list_b):
        # choose smaller of the 2 items and add it to the merged list
        if list_a[list_a_index] <= list_b[list_b_index]:
            merged_list.append(list_a[list_a_index])
            list_a_index += 1
        else:
            merged_list.append(list_b[list_b_index])
            list_b_index += 1

    # Grab any lingering items in the first list after we've exhaused the second list
    while list_a_index < len(list_a):
        merged_list.append(list_a[list_a_index])
        list_a_index += 1

    # Grab any lingering items in the second list after we've exhaused the first list
    while list_b_index < len(list_b):
        merged_list.append(list_b[list_b_index])
        list_b_index += 1

    return merged_list