from typing import List
import re


def tokenize(arg: str) -> List[str]:
    """
    Tokenize.

    >>> tokenize("1+2+42")
    ['1', '+', '2', '+', '42']

    >>> tokenize("(1 + 2) * 3")
    ['(', '1', '+', '2', ')', '*', '3']
    """
    return (
        re.sub("([0-9]+)", r" \1 ", arg)
        .replace("(", " ( ")
        .replace(")", " ) ")
        .replace(",", " ")
        .split()
    )