#[macro_export]
macro_rules! setup {
    { mut $input:ident: SplitWhitespace $(,)? } => {
        use std::io::Read;
        let mut buf = String::new();
        std::io::stdin().read_to_string(&mut buf).ok();
        let mut $input = buf.split_whitespace();
    };
}

#[macro_export]
macro_rules! parse_next {
    ($str_iter:expr) => {
        $str_iter.next().unwrap().parse().ok().unwrap()
    };
}

fn main() {
    setup! { mut input: SplitWhitespace };

    let n: usize = parse_next!(input);
    let a: Vec<i64> = (0..(2 * n)).map(|_| parse_next!(input)).collect();

    let mut b = vec![];
    for i in 0..n {
        b.push(a[2 * i + 1] - a[2 * i]);
    }

    let ans = (|| {
        let mut score = b.iter().sum::<i64>();
        let mut max = score;
        for i in 0..n {
            score += (b[i] * (-1)) * 2;
            max = score.max(max);
        }
        max
    })();

    println!("{}", ans);
}