#include <sstream>
#include <string>
#include <vector>
#include <map>
#include <algorithm>
#include <iostream>
#include <utility>
#include <set>
#include <cctype>
#include <queue>
#include <stack>
#include <cstdio>
#include <cstdlib>
#include <cmath>

#define INF 1000000000

using namespace std;
typedef long long ll;

const int MAXN = 100010;

int dfs(int d, vector<int>& v) {
    if (v.size() <= 1) return 0;
    vector<int> w[2];
    for (int i = 0; i < (int)v.size(); i++) {
        int x = v[i];
        w[(x>>d)&1].push_back(x^(x&(1<<d)));
    }
    if (w[0].empty()) return dfs(d-1, w[1]);
    if (w[1].empty()) return dfs(d-1, w[0]);
    return (1<<d) + min(dfs(d-1, w[0]), dfs(d-1, w[1]));
}

int main() {
    int N;
    cin >> N;
    set<int> s;
    for (int i = 0; i < N; i++) {
        int x;
        cin >> x;
        s.insert(x);
    }
    vector<int> v;
    for (auto it = s.begin(); it != s.end(); it++) {
        v.push_back(*it);
    }
    cout << dfs(30, v) << endl;
}