def uniqueValues(aDict):
    """
    Write a Python function that returns a list of keys in aDict that map
    to integer values that are unique (i.e. values appear exactly once in aDict).
    The list of keys you return should be sorted in increasing order.
    (If aDict does not contain any unique values, you should return an empty list.)
    """

    keep, already_seen = {}, set()
    for k, v in aDict.items():
        if v in already_seen:
            if v in keep:      # remove it, we have already see this
                del keep[v]
        else:                  # add it for now and store the key, keep track of what seen
            keep[v] = k
            already_seen.add(v)

    lista = list(keep.values())

    return sorted(lista)