use std::io::Read;

fn calc(a: &[u32], k: u32) -> u32 {
    if a.len() <= 1 || k == 0 {
        return 0;
    }
    let k = k - 1;
    if (a[0] ^ a.last().unwrap()) >> k & 1 == 0 {
        calc(a, k)
    } else {
        let x = a.iter().position(|a| *a >> k & 1 == 1).unwrap();
        let p = a.split_at(x);
        std::cmp::min(calc(p.0, k), calc(p.1, k)) + (1 << k)
    }
}

fn run() {
    let mut s = String::new();
    std::io::stdin().read_to_string(&mut s).unwrap();
    let mut it = s.trim().split_whitespace();
    it.next();
    let mut a: Vec<u32> = it.map(|s| s.parse().unwrap()).collect();
    a.sort();
    let ans = calc(&a, 30);
    println!("{}", ans);
}

fn main() {
    run();
}