#include <bits/stdc++.h>
using namespace std;

int main(){
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);

    int N; cin >> N;
    vector<int> A(N);
    for(auto &a : A) cin >> a;

    vector<int> odd(N),even(N);
    for(int i=0; i<N; i++) for(int d=0; d<30; d++){
        int a = (A.at(i)>>d)&1;
        if(d%2) odd.at(i) += a<<d,even.at(i) += 1<<d;
        else even.at(i) += a<<d;
    }
    int start = 0;
    for(int d=0; d<30; d+=2) start += 1<<d;

    vector<bool> alive(N,true);
    int answer = 0;
    for(int d=29; d>=0; d--){
        answer += 1<<d;
        if(d%2 == 0){
            int now = start,pick = 0;
            for(int i=0; i<N; i++) if(alive.at(i)){
                int a = (A.at(i)>>d)&1;
                if(a) now |= odd.at(i),now &= even.at(i),pick++;
            }
            if(pick && ((now&answer) == answer)){
                for(int i=0; i<N; i++) if(alive.at(i)){
                    int a = (A.at(i)>>d)&1;
                    if(a == 0) alive.at(i) = false;
                }
            }
            else answer -= 1<<d;
        }
        else{
            int pick = 0;
            for(int i=0; i<N; i++) if(alive.at(i)){
                int a = (A.at(i)>>d)&1;
                if(a) pick++;
            }
            if(pick == 0) answer -= 1<<d;
        }
    }
    cout << answer << endl;
}