#include <sstream>
#include <string>
#include <vector>
#include <map>
#include <algorithm>
#include <iostream>
#include <utility>
#include <set>
#include <cctype>
#include <queue>
#include <stack>
#include <cstdio>
#include <cstdlib>
#include <cmath>

#define INF 1000000000

using namespace std;
typedef long long ll;

const int MAXN = 100010;
int a[MAXN];
bool bit[64];

int main(void) {
    int N;
    cin >> N;
    for (int i = 0; i < N; i++) cin >> a[i];
    for (int i = 0; i < 32; i++) {
        bit[i] = true;
    }
    for (int i = 0; i < 32; i++) {
        for (int j = 0; j < N; j++) {
            if (((a[j] >> i) & 1) == 0) bit[i] = false;
        }
    }
    int ans = 0;
    for (int i = 0; i < 32; i++) {
        if (bit[i]) ans |= 1<<i;
    }
    int ret = 0;
    for (int i = 0; i < N; i++) {
        ret = max(a[i] ^ ans, ret);
    }
    cout << ret << endl;
    return 0;
}