use proconio::input;

fn main() {
    input! {
        n: usize,
        h: usize,
        ab: [(usize, usize); n],
    }

    let mut memo = vec![0; h + 1];
    let mut cnt = 0;
    for &(a, b) in &ab {
        if b - a > h / 2 {
            memo[0..a].iter_mut().for_each(|x| *x -= 1);
            memo[b + 1..=h].iter_mut().for_each(|x| *x -= 1);
            cnt += 1;
        } else {
            memo[a..=b].iter_mut().for_each(|x| *x += 1);
        }
    }

    println!("{}", memo.iter().max().unwrap() + cnt);
}