import collections


def merge_dicts(dict1: dict, dict2: dict) -> dict:
    """
    Merges two dicts adding up the values.

    :param dict1: The first dict.
    :param dict2: The second dict.
    :return: A dict with the added values of first and second dicts.
    """
    return dict(collections.Counter(dict1) + collections.Counter(dict2))