#include <iostream>
#include <vector>
#include <memory>
#define repeat(i,n) for (int i = 0; (i) < (n); ++(i))
using namespace std;
struct tree_t {
    shared_ptr<tree_t> left, right;
};
shared_ptr<tree_t> insert(shared_ptr<tree_t> t, int32_t x, int i) {
    if (not t) t = make_shared<tree_t>();
    if (i == -1) return t;
    shared_ptr<tree_t> & nt = (x & (1 << i) ? t->right : t->left);
    nt = insert(nt, x, i-1);
    return t;
}
int dfs(shared_ptr<tree_t> const & t, int i) {
    return
        not t ? 0 :
        not t->left  ? dfs(t->right, i-1) :
        not t->right ? dfs(t->left, i-1) :
        min(dfs(t->left, i-1), dfs(t->right, i-1)) + (1 << i);
}
int main() {
    int n; cin >> n;
    vector<int32_t> a(n); repeat (i,n) cin >> a[i];
    shared_ptr<tree_t> root = nullptr;
    repeat (i,n) root = insert(root, a[i], 31);
    cout << dfs(root, 31) << endl;
    return 0;
}