use std::cmp::max;
use std::io::*;

fn main() {
    let mut s: String = String::new();
    std::io::stdin().read_to_string(&mut s).ok();
    let mut itr = s.trim().split_whitespace();
    let n: usize = itr.next().unwrap().parse().unwrap();
    let a: Vec<i64> = (0..n * 2)
        .map(|_| itr.next().unwrap().parse().unwrap())
        .collect();
    let mut even = vec![0; n + 1];
    let mut odd = vec![0; n + 1];
    for i in 0..n {
        even[i + 1] = even[i] + a[i * 2];
        odd[i + 1] = odd[i] + a[i * 2 + 1];
    }

    let mut ans = 0;
    for l in 0..n + 1 {
        let left = even[l] - odd[l];
        let right = (odd[n] - odd[l]) - (even[n] - even[l]);
        ans = max(ans, left + right);
    }
    println!("{}", ans);
}