use std::io::Read;

fn main() {
	let mut s = String::new();
	std::io::stdin().read_to_string(&mut s).ok();
	let mut s = s.trim().split_whitespace();
	let _n: usize = s.next().unwrap().parse().unwrap();
	let v: Vec<usize> = s.map(|e| e.parse().unwrap()).collect();
	
	let (mut a, mut b, mut c) = (0usize, 0usize, 0usize);
	for i in v {
		c = b + i;
		b = if a > b { a } else { b };
		a = c;
	}
	println!("{}", if a > b { a } else { b });
}