def merge_two_lists(list_one, list_two):
    """
    Function merge two lists in a list. Then return the sorted list.
    Input lists don't change.

    :rtype: list
    :return: sorted list
    """

    # Copy lists by value
    temp_list_one = list_one[:]
    temp_list_two = list_two[:]

    mergedlist = []
    while temp_list_one and temp_list_two:
        if temp_list_one[0] <= temp_list_two[0]:
            mergedlist.append(temp_list_one.pop(0))
        else:
            mergedlist.append(temp_list_two.pop(0))

    while temp_list_one:
        mergedlist.append(temp_list_one.pop(0))

    while temp_list_two:
        mergedlist.append(temp_list_two.pop(0))

    return mergedlist