#include<bits/stdc++.h>
using namespace std;
#include<atcoder/all>
using namespace atcoder;
using ll = long long;
ll n;
vector<ll> a;

ll dp[40][2];
ll dpx[40][2];

void solve(){
	for(ll i = 40-2;i>=0;i--){
		for(ll j = 0;j<2;j++){//to
			ll mn = LLONG_MAX/2;
			for(ll k = 0;k<2;k++){//from
				auto b = a;
				for(auto &l :b)l ^= dpx[i+1][k]+(j<<i);
				ll mnb = b[0];
				for(auto &l:b)mnb = max(mnb,l);
				if(mn>mnb){
					mn = mnb;
					dpx[i][j] = dpx[i+1][k] + (j<<i);
				}
			}
		}
	}
	ll mn = LLONG_MAX/2;
	{
		auto b = a;
		for(auto &l:b)l ^= dpx[0][0];
		ll mxb = b[0];
		for(auto &l:b)mxb = max(l,mxb);
		mn = min(mn,mxb);
	}
	{
		auto b = a;
		for(auto &l:b)l ^= dpx[0][1];
		ll mxb = b[0];
		for(auto &l:b)mxb = max(l,mxb);
		mn = min(mn,mxb);
	}
	//cout<<dpx[0][0] << ' '<<dpx[0][1]<<endl;
	cout<<mn<<endl;
	
}

signed main(){
	cin.tie(nullptr);
	ios::sync_with_stdio(false);
	cin >> n;
	a = vector<ll>(n);
	for(auto &i:a)cin >> i;
	solve();
}