/* -*- coding: utf-8 -*-
 *
 * 130.cc: No.130 XOR Minimax - yukicoder
 */

#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<cmath>
#include<iostream>
#include<string>
#include<vector>
#include<map>
#include<set>
#include<stack>
#include<list>
#include<queue>
#include<deque>
#include<algorithm>
#include<numeric>
#include<utility>
#include<complex>
#include<functional>
 
using namespace std;

/* constant */

const int MAX_N = 100000;
const int MAX_B = 31;

/* typedef */

/* global variables */

int as[MAX_N], zs[MAX_B], os[MAX_B];

/* subroutines */

/* main */

int main() {
  int n;
  cin >> n;
  for (int i = 0; i < n; i++) cin >> as[i];

  int maxa = 0;
  for (int i = 0; i < n; i++) {
    int &ai = as[i];
    if (maxa < ai) maxa = ai;
    for (int j = 0, bj = 1; j < MAX_B; j++, bj <<= 1) {
      if (ai & bj) os[j]++;
      else zs[j]++;
    }
  }

  int ans = 0;
  for (int j = 0, bj = 1; j < MAX_B; j++, bj <<= 1)
    if (zs[j] && os[j]) ans |= bj;

  printf("%d\n", min(ans, maxa));
  return 0;
}