#include <bits/stdc++.h>
using namespace std;

int dfs(int x, vector<int>& A) {
    if (A.size() <= 1)
        return 0;

    vector<int> V[2];
    for (auto& a : A) {
        V[!!(a & (1 << x))].emplace_back(a);
    }


    if (V[0].empty())
        return dfs(x - 1, V[1]);
    if (V[1].empty())
        return dfs(x - 1, V[0]);

    return (1 << x) + min(dfs(x - 1, V[0]), dfs(x - 1, V[1]));
}

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

    sort(A.begin(), A.end());
    A.erase(unique(A.begin(), A.end()), A.end());

    cout << dfs(30, A) << endl;
}