#include<queue>
#include<math.h>
#include<stdio.h>
#include<iostream>
#include<vector>
#include<iomanip>
#include<string.h>
#include<algorithm>
#include<cmath>
#include<cstdio>
#include<utility>
#include<cstring>
#include<stack>
#include<fstream>
#include <sstream>
#include<string>
#include<stdlib.h>
using namespace std;
#define ll long long
const int N = 1e6 + 10;
const int INF = 0x3f3f3f3f;
int aa;
int main()
{
    int n , one = 0 , two = 0 , three = 0;
    cin >> n;
    for ( int i = 1 ; i <= n ; i++ )
    {
        cin >> aa;
        two ^= ( one & aa );
        one ^= aa;
        three =~ ( one & two );
        two &= three;
        one &= three;
    }
    cout << one;
    return 0;
}

感谢huhe(小小苦力怕)http://temege.com/user/698