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 {
            for j in 0..a {
                memo[j] -= 1;
            }
            for j in b + 1..=h {
                memo[j] -= 1;
            }
            cnt += 1;
        } else {
            for i in a..=b {
                memo[i] += 1;
            }
        }
    }

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