#pragma GCC optimize1#pragma GCC optimize2#pragma GCC optimize3Ofastinline#includebitsstdc++husing namespace std;inline static const nullptr_t _ = ios_basesync_with_stdio0; cintienullptr coutt

import * as readline from 'readline';

const rl = readline.createInterface({ input: process.stdin, output: process.stdout, });

let n: number; let x: number; let a: number; let ret: number;

rl.on('line', (line) => { const inputs = line.split(' '); n = parseInt(inputs[0]); x = parseInt(inputs[1]); });

rl.on('line', (line) => { const inputs = line.split(' '); ret = -Infinity; for (let i = 0; i < n; i++) { a = parseInt(inputs[i]); ret = Math.max(ret, a | x); } console.log(ret); })