// ---------- begin next_permutation ----------
fn next_permutation<T: Ord>(a: &mut [T]) -> bool {
    a.windows(2).rposition(|a| a[0] < a[1]).map_or(false, |x| {
        let y = a.iter().rposition(|b| a[x] < *b).unwrap();
        a.swap(x, y);
        a[(x + 1)..].reverse();
        true
    })
}
// ---------- end next_permutation ----------

fn read() -> Vec<u32> {
    let mut s = String::new();
    use std::io::Read;
    std::io::stdin().read_to_string(&mut s).unwrap();
    let mut it = s.trim().split_whitespace();
    let mut next = || it.next().unwrap().parse::<u32>().unwrap();
    let n = next();
    (0..n).map(|_| next()).collect()
}

fn main() {
    let mut a = read();
    a.sort();
    let mut ans = 0;
    while {
        let mut xor = 0;
        for a in a.chunks_exact_mut(2) {
            xor ^= a[0] + a[1];
            a.sort_by_key(|a| !*a);
        }
        ans = ans.max(xor);
        next_permutation(&mut a)
    } {}
    println!("{}", ans);
}