#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;
        int mask = s | 1<<i;
        REP(j,N){
            v = max(v, A[j] ^ mask);
        }
        if(v < maxv){
            maxv = v;
            s = mask;
        }
    }
    cerr << s << endl;
    cout << maxv << endl;
}