from typing import Union
from typing import List


def add_n(obj: Union[int, List], n: int) -> Union[int, List]:
    """Return a new nested list where <n> is added to every item in <obj>.

    >>> add_n(10, 3)
    13
    >>> add_n([1, 2, [1, 2], 4], 10)
    [11, 12, [11, 12], 14]
    """
    if isinstance(obj, int):
        return obj + n
    else:
        new_list = []
        for sublist in obj:
            new_list.append(add_n(sublist, n))
    return new_list