#include <iostream>
#include <vector>
using namespace std;

using uint = unsigned int;

uint f(int i, vector<uint>& A) {
    if (i < 0) {
        return 0;
    }
    vector<uint> A1, A2;
    for (uint a : A) {
        if (((a >> i) & 1)) A1.emplace_back(a);
        else A2.emplace_back(a);
    }
    if (A2.empty()) return f(i - 1, A1);
    else if (A1.empty()) return f(i - 1, A2);
    else return min((1 << i) | f(i - 1, A1), (1 << i) | f(i - 1, A2));
}

int main() {
    int N;
    cin >> N;

    vector<uint> a(N);
    for (int i = 0; i < N; i++) {
        cin >> a[i];
    }

    cout << f(31, a) << endl;

    return 0;
}