use std::cmp::max; fn main() { let mut n = String::new(); std::io::stdin().read_line(&mut n).ok(); let n: usize = n.trim().parse().unwrap(); let mut a = String::new(); std::io::stdin().read_line(&mut a).ok(); let a: Vec<usize> = a.trim().split_whitespace().map(|s| s.parse().unwrap()).collect(); let mut result: usize = 0; for i in 0..n { for j in i..n { result = max(result, a[i] ^ a[j]); } } println!("{}", result); }