use std::io::Read;
use std::cmp;

fn main() {
    let mut buf = String::new();
    std::io::stdin().read_to_string(&mut buf).unwrap();
    
    let mut iter = buf.split_whitespace();
    
    let n: usize = iter.next().unwrap().parse().unwrap();
    let sushi_lane: Vec<usize> = iter
        .map(|v| v.parse::<usize>().unwrap())
        .collect();
    
    println!("{}", calc_max(&sushi_lane, 0, n-1));
}

fn calc_max(sushi_lane: &Vec<usize>, pos: usize, tail: usize) -> usize {
    if pos == tail {
        return sushi_lane[tail]
    } else if pos > tail {
        return 0
    }
    
    let left_max: usize = sushi_lane[pos] + calc_max(sushi_lane, pos+2, tail);
    let right_max: usize = sushi_lane[pos+1] + calc_max(sushi_lane, pos+3, tail);

    cmp::max(left_max, right_max)
}