#include <bits/stdc++.h>
using namespace std;
/*{{{*/  //template
#define rep(i,n) for(int i=0;i<(int)(n);i++)
#define rrep(i,n) for(int i=(n)-1;i>=0;i--)
constexpr int INF = numeric_limits<int>::max()/2;
constexpr long long LINF = numeric_limits<long long>::max()/3;
#define pb push_back
#define eb emplace_back
#define fi first
#define se second
#define all(v) (v).begin(),(v).end()
#define sz(x) (int)(x).size()
#define debug(x) cerr<<#x<<":"<<x<<endl
#define debug2(x,y) cerr<<#x<<","<<#y":"<<x<<","<<y<<endl
//struct fin{ fin(){ cin.tie(0); ios::sync_with_stdio(false); } } fin_;
struct Double{ double d; explicit Double(double x) : d(x){} };
ostream& operator<<(ostream& os,const Double x){ os << fixed << setprecision(20) << x.d; return os; }
template<typename T> ostream& operator<<(ostream& os,const vector<T>& vec){ os << "["; for(const auto& v : vec){ os << v << ","; } os << "]"; return os; }
template<typename T,typename U> ostream& operator<<(ostream& os, const map<T,U>& mp){ os << "{"; for(auto& p : mp){ os << p << ","; } os << "}"; return os; }
template<typename T,typename U> ostream& operator<<(ostream& os,const pair<T,U>& p){ os << "(" << p.first << ","<< p.second <<")"; return os; }
template<typename T> ostream& operator<<(ostream& os,const set<T>& st){ os<<"{"; for(T v:st) os<<v<<","; os <<"}"; return os; }
template<typename T,typename U> inline void chmax(T &x,U y){ if(y>x) x = y; }
template<typename T,typename U> inline void chmin(T &x,U y){ if(y<x) x = y; }
using ll = long long;
using ull = unsigned long long;
using pii = std::pair<int,int>;
using vi = std::vector<int>;
typedef vector<vi> vvi;
ll gcd(ll a,ll b){ if(b==0) return a; else return gcd(b,a%b); }
constexpr ll TEN(int n) { return (n == 0) ? 1 : 10 * TEN(n - 1); }
//constexpr double eps = 1e-14; 
constexpr double eps = 1e-10; 
constexpr ll mod = 1e9+7;
const int dx[]={1,0,-1,0} ,dy[] = {0,1,0,-1};
/*}}}*/


// xのt-bit目を確定する. その時の最大値
int f(int x,int t,vector<int>& v){
    /* cout << bitset<32>(x) << " " << t << " " << v << endl; */
    int n = v.size();

    if(t==0){
        int ret1 = 0;
        int ret2 = 0;
        for(int i=0;i<n;i++){
            ret1 = max(ret1, x^v[i]);
            ret2 = max(ret2, (x|(1<<t))^v[i]);
        }
        return min(ret1,ret2);
    }

    vector<int> b,c;
    for(int i=0;i<n;i++){
        if(v[i] & (1<<t)){ // 1
            b.emplace_back(v[i]);
        }else{ // 0
            c.emplace_back(v[i]);
        }
    }

    /* cout << "b : " << b << endl; */
    /* cout << "c : " << c << endl; */

    if(b.size() == n){
        return f(x|(1<<t), t-1, b);
    }
    else if(c.size() == n){
        return f(x,t-1, c);
    }
    else{
        int mx1 = (b.size() > 0) ? f(x,t-1,b) : INF;
        int mx2 = (c.size() > 0) ? f(x|(1<<t),t-1,c) : INF;
        return min(mx1,mx2);
    }
}

int main(){
    int n;
    vector<int> a;
    cin >> n;
    a.resize(n); rep(i,n) cin >> a[i];
    cout << f(0, 30, a) << endl;
}