#include <bits/stdc++.h>
using namespace std;
#define rep(i, n) for (int i = 0; i < (n); i++)
using ll = long long;
using vll = vector<ll>;
using vi = vector<int>;
using vvi = vector<vector<int>>;
using vvll = vector<vector<ll>>;
const ll inf = 1e16;
const ll md = 1000000007;

int bitlen(ll x){
  int i=32;
  while (true){
    if(x>>i&1) return i;
    i--;
  }
}


int main() {
  int n;
  cin >> n;
  vll a(n);
  rep(i,n) cin>>a[i];
  ll mx=0LL;
  rep(i,n) mx=max(mx,a[i]);
  rep(i,n) a[i]=a[i]^mx;
  sort(a.begin(),a.end());
  auto ei=unique(a.begin(),a.end());
  n=ei-a.begin();
  if(n==1){
    puts("0");
    return 0;
  }
  vector<bool> sep(n+1);
  sep[0]=true;
  sep[n]=true;
  int ti=bitlen(*(ei-1));
  int ans=0;
  for(int i=ti;i>=0;i--){
    ans+=1<<i;
    int pre=0;
    rep(j,n){
      int now=a[j]>>i&1;
      if(pre==0&&now){
        sep[j]=true;
        if(sep[j-1]){
          cout<<ans<<endl;
          return 0;
        }
      }
      pre=now;
    }
  }
  return 0;
}