#include <bits/stdc++.h>
using namespace std;
typedef unsigned int ui;
#define REP(i, n) for(int(i)=0;(i)<(n);++(i))
int A[100100];
int main(){
    int N; cin >> N;
    int maxv = 0;
    REP(i,N){
        cin >> A[i];
        maxv = max(maxv, A[i]);
    }
    int s = 0;
    for(int i = 30; i >= 0; i--){
        int v = 0;
        for(int k = 1; k <= 3; k++){
            int mask = s | (k<<i);
            REP(j,N){
                v = max(v, A[j] ^ mask);
            }
            if(v < maxv){
                maxv = v;
                s = mask;
            }
        }
    }
    cerr << s << endl;
    cout << maxv << endl;
}