#![allow(unused_imports)]
#![allow(non_snake_case)]
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()
}

trait IteratorExt: Iterator + Sized {
    fn vec(self) -> Vec<Self::Item> {
        self.collect()
    }
}
impl<T: Iterator> IteratorExt for T {}

fn main() {
    let _ = read!(usize; 1);
    let v = read!([usize]);

    // 動的計画法が怪しい
    println!("{}", max_score(&v));
}

fn max_score(s: &[usize]) -> usize {
    if s.len() == 0 {return 0;}

    let a = {
        if s.len() < 2 {
            s[0]
        }
        else {
            s[0] + max_score(&s[2..])
        }
    };
    let b = max_score(&s[1..]);

    a.max(b)
}