#define _USE_MATH_DEFINES
 
#include <iostream>
#include <iomanip>
#include <sstream>
 
#include <algorithm>
#include <cmath>
 
#include <string>
//#include <array>
#include <list>
#include <queue>
#include <vector>
#include <complex>
#include <set>
#include <map>
 
/////////
#define REP(i, x, n) for(int i = x; i < n; i++)
#define rep(i,n) REP(i,0,n)
#define P(p) cout<<(p)<<endl;
 
#define PII pair<int,int>
/////////
typedef long long LL;
typedef long double LD;
/////////
using namespace::std;
/////////
int A[(int)1e5];

int main(void){
    std::cin.tie(0); 
    std::ios::sync_with_stdio(false);
    std::cout << std::fixed;//
    cout << setprecision(16);//
	
	int N;
	cin>>N;
	rep(i,N){
		cin>>A[i];
	}
	int tmin = (int)1e9+1;
	int temp;
	int Lmax;
	rep(i,N){
		Lmax = 0;
		rep(j,N){
			temp = A[i] ^ A[j];
			Lmax = max(Lmax,temp);
			if(tmin < Lmax){
				break;
			}
		}
		tmin = min(tmin,Lmax);
	}
	P(tmin);
	return 0;
}