import unittest


def merge_ranges(xs):
    xs.sort()
    result = [xs[0]]
    for curr in xs[1:]:
        a, z = result[-1]
        if z >= curr[0]:
            result[-1] = (a, max(z, curr[1]))
        else:
            result.append(curr)
    return result


# Tests
class Test(unittest.TestCase):
    def test_meetings_overlap(self):
        actual = merge_ranges([(1, 3), (2, 4)])
        expected = [(1, 4)]
        self.assertEqual(actual, expected)

    def test_meetings_touch(self):
        actual = merge_ranges([(5, 6), (6, 8)])
        expected = [(5, 8)]
        self.assertEqual(actual, expected)

    def test_meeting_contains_other_meeting(self):
        actual = merge_ranges([(1, 8), (2, 5)])
        expected = [(1, 8)]
        self.assertEqual(actual, expected)

    def test_meetings_stay_separate(self):
        actual = merge_ranges([(1, 3), (4, 8)])
        expected = [(1, 3), (4, 8)]
        self.assertEqual(actual, expected)

    def test_multiple_merged_meetings(self):
        actual = merge_ranges([(1, 4), (2, 5), (5, 8)])
        expected = [(1, 8)]
        self.assertEqual(actual, expected)

    def test_meetings_not_sorted(self):
        actual = merge_ranges([(5, 8), (1, 4), (6, 8)])
        expected = [(1, 4), (5, 8)]
        self.assertEqual(actual, expected)

    def test_one_long_meeting_contains_smaller_meetings(self):
        actual = merge_ranges([(1, 10), (2, 5), (6, 8), (9, 10), (10, 12)])
        expected = [(1, 12)]
        self.assertEqual(actual, expected)

    def test_sample_input(self):
        actual = merge_ranges([(0, 1), (3, 5), (4, 8), (10, 12), (9, 10)])
        expected = [(0, 1), (3, 8), (9, 12)]
        self.assertEqual(actual, expected)


unittest.main(verbosity=2)