// Standard I/O
#include <iostream>
#include <sstream>
#include <cstdio>
// Standard Library
#include <cstdlib>
#include <cstring>
#include <ctime>
#include <cmath>
// Template Class
#include <complex>
#include <string>
#include <vector>
#include <list>
#include <set>
#include <map>
#include <queue>
#include <stack>
// Container Control
#include <algorithm>

using namespace std;

#define rep( i, n ) for( int i = 0; i < n; ++i )
#define irep( i, n ) for( int i = n-1; i >= 0; --i )
#define reep( i, s, n ) for ( int i = s; i < n; ++i )
#define ireep( i, n, s ) for ( int i = n-1; i >= s; --i )
#define foreach(itr, x) for( typeof(x.begin()) itr = x.begin(); itr != x.end(); ++itr)

#define mp( a, b ) make_pair( a, b )
#define pb( a ) push_back( a )
#define all( v ) v.begin(), v.end()
#define fs first
#define sc second
#define vc vector

// for visualizer.html
double SCALE = 1.0;
double OFFSET_X = 0.0;
double OFFSET_Y = 0.0;
#define LINE(x,y,a,b) cerr << "line(" << SCALE*(x) + OFFSET_X << ","	\
	<< SCALE*(y) + OFFSET_Y << ","										\
	<< SCALE*(a) + OFFSET_X << ","										\
	<< SCALE*(b) + OFFSET_Y << ")" << endl;
#define CIRCLE(x,y,r) cerr << "circle(" << SCALE*(x) + OFFSET_X << ","	\
	<< SCALE*(y) + OFFSET_Y << ","										\
	<< SCALE*(r) << ")" << endl;

typedef long long ll;
typedef complex<double> Point;

typedef pair<int, int> pii;
typedef pair<int, pii> ipii;
typedef vector<int> vi;
typedef vector<double> vd;
typedef vector< vector<int> > vii;
typedef vector< vector<double> > vdd;

typedef vector<int>::iterator vi_itr;

const int IINF = 1 << 28;
const double INF = 1e30;
const double EPS = 1e-10;
const double PI = acos(-1.0);

// Direction : L U R D
const int dx[] = { -1, 0, 1, 0};
const int dy[] = { 0, -1, 0, 1 };

int N;
ll a[100000];
ll solve ( int d, ll x )
{
	if( d == 0 ){
		ll ans[2] = { 0 };

		rep(i, N) ans[0] = max(ans[0], a[i]^x);
		rep(i, N) ans[1] = max(ans[1], a[i]^(x | 1));
		
		return min(ans[0], ans[1]);
	}

	ll num = 0;
	rep(i, N) if( (a[i] & (1ll << d)) != 0 ) ++num;

	if( num == N ) return solve(d-1, x | (1ll << d));
	else return solve(d-1, x);
}

int main()
{
	cin >> N;
	rep(i, N) cin >> a[i];

	cout << solve(31, 0) << endl;
}