fn main() {
    proconio::input! {
        n: usize,
        a: [i64; n*2],
    }
    let points = a.chunks_exact(2).map(|x| x[1] - x[0]).collect::<Vec<_>>();
    eprintln!("{points:?}");
    let mut lpoint = 0;
    let mut rpoint = points.iter().sum::<i64>();
    let mut point_max = lpoint + rpoint;
    for i in 0..points.len() {
        lpoint -= points[i];
        rpoint -= points[i];
        point_max = std::cmp::max(point_max, lpoint + rpoint);
    }
    println!("{}", point_max);
}