import re


def find_explodable(number: str) -> re.Match[str] | None:
    """
    Finds the first pair nested inside four pairs and returns a Match object
    or None, if there are no such pairs
    """
    for match in re.finditer(r"(\[(?P<first>\d+),(?P<second>\d+)\])", number):
        before_match = number[: match.start()]
        if before_match.count("[") - before_match.count("]") >= 4:
            return match
    return None