#![allow(dead_code)]
#![allow(unused_imports)]
#![allow(unused_mut)]
#![allow(unused_macros)]
#![allow(unused_variables)]
#![allow(non_upper_case_globals)]
#![allow(non_snake_case)]
#![allow(unused_unsafe)]
#![allow(unused_must_use)]
use std::cmp::*;
use std::collections::*;
use std::io::{self, stdout, BufRead, BufWriter, Write};

macro_rules! input {
    (source = $s:expr, $($r:tt)*) => {
        let mut iter = $s.split_whitespace();
        input_inner!{iter, $($r)*}
    };
    ($($r:tt)*) => {
        let s = {
            use std::io::Read;
            let mut s = String::new();
            std::io::stdin().read_to_string(&mut s).unwrap();
            s
        };
        let mut iter = s.split_whitespace();
        input_inner!{iter, $($r)*}
    };
}

macro_rules! input_inner {
    ($iter:expr) => {};
    ($iter:expr, ) => {};
    ($iter:expr, $var:ident : $t:tt $($r:tt)*) => {
        let $var = read_value!($iter, $t);
        input_inner!{$iter $($r)*}
    };
}

macro_rules! read_value {
    ($iter:expr, ( $($t:tt),* )) => {
        ( $(read_value!($iter, $t)),* )
    };
    ($iter:expr, [ $t:tt ; $len:expr ]) => {
        (0..$len).map(|_| read_value!($iter, $t)).collect::<Vec<_>>()
    };
    ($iter:expr, chars) => {
        read_value!($iter, String).chars().collect::<Vec<char>>()
    };
    ($iter:expr, bytes) => {
        read_value!($iter, String).bytes().collect::<Vec<u8>>()
    };
    ($iter:expr, usize1) => {
        read_value!($iter, usize) - 1
    };
    ($iter:expr, $t:ty) => {
        $iter.next().unwrap().parse::<$t>().expect("Parse error")
    };
}

macro_rules! dd {
    ($($a:expr),* $(,)*) => {
        #[cfg(debug_assertions)]
        eprintln!(concat!($("\x1b[38;5;39m|\x1b[m \x1b[38;5;39m", stringify!($a), " =\x1b[m {:?} "),*, "\x1b[38;5;69m|\x1b[m \x1b[38;5;6m"), $(&$a),*);
    };
}

macro_rules! w {
    ($output:expr, $x:expr) => {
        let _ = writeln!($output, "{}", $x);
    };
}

fn main() {
    let out = stdout();
    let mut out = BufWriter::new(out.lock());
    input!(n: usize, a: [usize; n]);

    let mut i = 0;
    for i in 0..usize::max_value() {
        let t = 1 << i;
        let mut valid = true;
        for j in 0..n {
            if a[j] & t != 0 {
                valid = false;
                break;
            }
        }

        if valid {
            w!(out, t);
            break;
        }
    }
}