public class Main1369 {
    public int countDays(int days, int[][] meetings) {
        Arrays.sort(meetings, Comparator.comparingInt(o -> o[0]));
        int hi = meetings[0][1];
        int res = meetings[0][0] - 1;
        for (int i = 1; i < meetings.length; i++) {
            int[] meeting = meetings[i];
            if (meeting[0] <= hi) {
                hi = Math.max(hi, meeting[1]);
            } else {
                res += (meeting[0] - hi - 1);
                hi = meeting[1];
            }
        }
        res += (days - hi);
        return res;
    }

    @Test
    public void test1() {
        int days = 10;
        int[][] meetings = {{5, 7}, {1, 3}, {9, 10}};
        int expected = 2; 
        assert countDays(days, meetings) == expected : "Test failed";
    }

    @Test
    public void test2() {
        int days = 5;
        int[][] meetings = {{2, 4}, {1, 3}};
        int expected = 1;
        assert countDays(days, meetings) == expected : "Test failed";
    }

    @Test
    public void test3() {
        int days = 6;
        int[][] meetings = {{1, 6}};
        int expected = 0;
        assert countDays(days, meetings) == expected : "Test failed";
    }
}