How does Python's super() work with multiple inheritance?

How does super() work with multiple inheritance? For example, given:

class First(object):
    def __init__(self):
        print "first"

class Second(object):
    def __init__(self):
        print "second"

class Third(First, Second):
    def __init__(self):
        super(Third, self).__init__()
        print "that's it"

Which parent method of Third does super().__init__ refer to? Can I choose which runs?

I know it has something to do with method resolution order (MRO).