/* -*- 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 = 30;

/* typedef */

typedef vector<int> vi;
typedef set<int> si;

/* global variables */

/* subroutines */

int rec(int k, vi &v) {
  if (v.size() <= 1) return 0;

  int bk = 1 << k;
  vi v0, v1;

  for (vi::iterator vit = v.begin(); vit != v.end(); vit++) {
    if (*vit & bk) v1.push_back(*vit ^ bk);
    else v0.push_back(*vit);
  }

  if (v1.size() == 0) return rec(k - 1, v0);
  if (v0.size() == 0) return rec(k - 1, v1);

  int r0 = rec(k - 1, v0);
  int r1 = rec(k - 1, v1);
  return (bk | min(r0, r1));
}

/* main */

int main() {
  int n;
  cin >> n;

  si sv;
  for (int i = 0; i < n; i++) {
    int ai;
    cin >> ai;
    sv.insert(ai);
  }

  vi v;
  for (si::iterator sit = sv.begin(); sit != sv.end(); sit++)
    v.push_back(*sit);

  printf("%d\n", rec(MAX_B - 1, v));
  return 0;
}