#include "bits/stdc++.h"
using namespace std;
#define FOR(i,j,k) for(int (i)=(j);(i)<(int)(k);++(i))
#define rep(i,j) FOR(i,0,j)
#define each(x,y) for(auto &(x):(y))
#define mp make_pair
#define all(x) (x).begin(),(x).end()
#define debug(x) cout<<#x<<": "<<(x)<<endl
#define smax(x,y) (x)=max((x),(y))
#define smin(x,y) (x)=min((x),(y))
#define MEM(x,y) memset((x),(y),sizeof (x))
#define sz(x) (int)(x).size()
typedef long long ll;
typedef pair<int, int> pii;
typedef vector<int> vi;
typedef vector<ll> vll;

int main(){
    vi flag(30);
    int N;
    cin >> N;
    vi a(N);
    rep(i, N)scanf("%d", &a[i]);
    rep(i, N){
        rep(j, 30)flag[j]|=(a[i] >> j & 1) ? 1 : 2;
    }
    int x = 0, ans = 0;
    rep(j, 30)if(flag[j] == 3)x |= 1 << j;
    rep(i, N)smax(ans, x^a[i]);
    smin(ans, *max_element(all(a)));
    cout << ans << endl;
}