#![allow(unused_imports)]
#![allow(non_snake_case)]
use std::collections::HashMap;
use std::collections::HashSet;
use std::collections::VecDeque;

#[allow(unused_macros)]
macro_rules! read {
    ([$t:ty] ; $n:expr) =>
        ((0..$n).map(|_| read!([$t])).collect::<Vec<_>>());
    ($($t:ty),+ ; $n:expr) =>
        ((0..$n).map(|_| read!($($t),+)).collect::<Vec<_>>());
    ([$t:ty]) =>
        (rl().split_whitespace().map(|w| w.parse().unwrap()).collect::<Vec<$t>>());
    ($t:ty) =>
        (rl().parse::<$t>().unwrap());
    ($($t:ty),*) => {{
        let buf = rl();
        let mut w = buf.split_whitespace();
        ($(w.next().unwrap().parse::<$t>().unwrap()),*)
    }};
}

#[allow(dead_code)]
fn rl() -> String {
    let mut buf = String::new();
    std::io::stdin().read_line(&mut buf).unwrap();
    buf.trim_end().to_owned()
}

fn main() {
    let n = read!(usize);
    let v = read!([isize]);
    let mut table_l = vec![0isize; n+1];
    let mut table_r = vec![0isize; n+1];
    for i in 0..n {
        table_l[i+1] = table_l[i] + v[i*2] - v[i*2+1];
        table_r[(n-1)-i] = table_r[(n-1)-i+1] + v[2*n-1-(i*2)] - v[2*n-1-(i*2+1)];
    }
    let max = table_l.iter().zip(table_r.iter()).max_by_key(|e| e.0 + e.1).unwrap();
    println!("{}", max.0 + max.1);
}