use proconio::input;

fn main() {
    input! {
        n:usize,
        mut r:[(usize,usize);n],
    }

    r.sort();
    let mut indegs = vec![0; n];
    let mut sorted_idx = (0..n).collect::<Vec<_>>();
    sorted_idx.sort_by(|i, j| r[*j].1.cmp(&r[*i].1));

    for i in sorted_idx {
        let id = r.lower_bound((r[i].1, 0));
        if id >= n || indegs[id] > 0 {
            continue;
        }

        indegs[id] += 1;
    }

    let ans = indegs.iter().filter(|indeg| **indeg == 0).count() - 1;
    println!("{}", ans);
}

use bound::*;
mod bound {
    pub trait Bound<T> {
        fn lower_bound(&self, val: T) -> usize;
        fn upper_bound(&self, val: T) -> usize;
    }

    impl<T> Bound<T> for [T]
    where
        T: Ord + Copy,
    {
        fn lower_bound(&self, val: T) -> usize {
            let mut ok = self.len();
            let mut ng = !0;
            while ok.wrapping_sub(ng) > 1 {
                let m = ok.wrapping_add(ng) / 2;
                if val <= self[m] {
                    ok = m;
                } else {
                    ng = m;
                }
            }

            ok
        }

        fn upper_bound(&self, val: T) -> usize {
            let mut ok = !0;
            let mut ng = self.len();
            while ng.wrapping_sub(ok) > 1 {
                let m = ng.wrapping_add(ok) / 2;
                if self[m] <= val {
                    ok = m;
                } else {
                    ng = m;
                }
            }

            ok
        }
    }
}