//#include <bits/stdc++.h>
#include <vector>
#include <string>
#include <queue>
#include <iostream>
#include <cstring>
#include <climits>
#define INF INT_MAX / 2
#define MOD 1000000007

using namespace std;

typedef pair<int,int> PII;
typedef pair<int,pair<int,int>> PIPII;
typedef long long ll;

int dx[] = {0,1,0,-1};
int dy[] = {1,0,-1,0};

ll combi(ll n,ll r){
    ll ret = 1;
    for(int i=n;i>n-r;i--){
        ret *= i;
        ret %= MOD;
    }
    for(int i=r;i>=1;i--){
        ret /= i;
    }
    return ret;
}

int main(void) {    
    int n;cin >> n;
    vector<int> a(n);
    for(int i=0;i<n;i++){
        cin >> a[i];
    }

    int b = 0;
    for(int i=0;i<10;i++){
        int cnt = 0;
        for(int j=0;j<n;j++){
            if((a[j]>>i) & 1)cnt++;
        }
        if(cnt == n)b |= (1<<i);
    }

    int ret = 0;
    for(int i=0;i<n;i++){
        ret = max(ret,a[i]^b);
    }
    cout << ret << endl;
    return 0;
}