def distribute_and_over_or(s):
    """Given a sentence s consisting of conjunctions and disjunctions
    of literals, return an equivalent sentence in CNF.
    >>> distribute_and_over_or((A & B) | C)
    ((A | C) & (B | C))
    """
    if s.op == '|':
        s = associate('|', s.args)
        if s.op != '|':
            return distribute_and_over_or(s)
        if len(s.args) == 0:
            return FALSE
        if len(s.args) == 1:
            return distribute_and_over_or(s.args[0])
        conj = find_if((lambda d: d.op == '&'), s.args)
        if not conj:
            return s
        others = [a for a in s.args if a is not conj]
        rest = associate('|', others)
        return associate('&', [distribute_and_over_or(c|rest)
                               for c in conj.args])
    elif s.op == '&':
        return associate('&', map(distribute_and_over_or, s.args))
    else:
        return s
Given a sentence s consisting of conjunctions and disjunctions
    of literals, return an equivalent sentence in CNF.
    >>> distribute_and_over_or((A & B) | C)
    ((A | C) & (B | C))