#include <bits/stdc++.h>

#define FOR(i, a, b) for (int i = (a); i < (b); i++)
#define RFOR(i, a, b) for (int i = (b)-1; i >= (a); i--)
#define rep(i, n) for (int i = 0; i < (n); i++)
#define rep1(i, n) for (int i = 1; i <= (n); i++)
#define rrep(i, n) for (int i = (n)-1; i >= 0; i--)

#define pb push_back
#define mp make_pair
#define fst first
#define snd second
#define show(x) cout << #x << " = " << x << endl
#define chmin(x, y) x = min(x, y)
#define chmax(x, y) x = max(x, y)
#define pii pair<int, int>
#define vi vector<int>

using namespace std;
template <class S, class T>
ostream& operator<<(ostream& o, const pair<S, T>& p)
{
    return o << "(" << p.first << "," << p.second << ")";
}
template <class T>
ostream& operator<<(ostream& o, const vector<T>& vc)
{
    o << "sz = " << vc.size() << endl
      << "[";
    for (const T& v : vc)
        o << v << ",";
    o << "]";
    return o;
}
using ll = long long;
constexpr ll MOD = 1000000007;

constexpr int MAX = 100000;
constexpr int LOG = 30;
bool bits[MAX][LOG];
bool rest[LOG];

void decode(ll a, int n)
{
    int i = 0;
    while (a > 0) {
        bits[n][i] = (a % 2);
        a /= 2;
        i++;
    }
}

int main()
{
    int N;
    cin >> N;
    rep(i, N)
    {
        ll a;
        cin >> a;
        decode(a, i);
    }

    rep(i, LOG)
    {
        bool c[2] = {false, false};
        rep(j, N)
        {
            c[bits[j][i]] = true;
        }
        if (c[0] and c[1]) {
            rest[i] = true;
        } else {
            rest[i] = false;
        }
    }

    ll m = 0;
    ll p = 1;
    rep(i, LOG)
    {
        if (rest[i]) {
            m += p * (ll)rest[i];
        }
        p *= 2;
    }
    cout << m << endl;

    return 0;
}