import unittest


def can_two_movies_fill_flight(xs, t):
    seeking = set()
    for x in xs:
        if x in seeking:
            return True
        else:
            seeking.add(t - x)
    return False


# Tests


class Test(unittest.TestCase):
    def test_short_flight(self):
        result = can_two_movies_fill_flight([2, 4], 1)
        self.assertFalse(result)

    def test_long_flight(self):
        result = can_two_movies_fill_flight([2, 4], 6)
        self.assertTrue(result)

    def test_one_movie_half_flight_length(self):
        result = can_two_movies_fill_flight([3, 8], 6)
        self.assertFalse(result)

    def test_two_movies_half_flight_length(self):
        result = can_two_movies_fill_flight([3, 8, 3], 6)
        self.assertTrue(result)

    def test_lots_of_possible_pairs(self):
        result = can_two_movies_fill_flight([1, 2, 3, 4, 5, 6], 7)
        self.assertTrue(result)

    def test_not_using_first_movie(self):
        result = can_two_movies_fill_flight([4, 3, 2], 5)
        self.assertTrue(result)

    def test_only_one_movie(self):
        result = can_two_movies_fill_flight([6], 6)
        self.assertFalse(result)

    def test_no_movies(self):
        result = can_two_movies_fill_flight([], 2)
        self.assertFalse(result)


unittest.main(verbosity=2)