/* 
 *     Author:  srtry
 *     Created: 2025-05-05T04:12:28+09:00
 *     Coding:  utf-8-unix
 */

use proconio::input;
use std::io::{stdout,Write,BufWriter};
use std::collections::HashSet;

fn main() {
    input!{
        n:usize,
        mut v:[usize;n]
    }
    v.insert(0,0);
    let v = v;

    let out = stdout();
    let mut out = BufWriter::new(out.lock());
    
    let mut dp:Vec<[usize;2]> = vec![[0,0];n+1];

    for i in 0..=n-1 {
        dp[i+1][0] = dp[i][0].max(dp[i][1]);
        dp[i+1][1] = dp[i][0] + v[i+1];
    }
    let ans:usize = dp[n][0].max(dp[n][1]);
    

    write!(out, "{}", ans).unwrap();
}