#include <bits/stdc++.h>

using namespace std;

vector<int> a;
int f(vector<int>& v, int bit) {
    if (v.empty() || bit < 0) return 0LL;

    vector<int> l, r;
    for (int& x : v) {
        if ((x >> bit) & 1) r.push_back(x);
        else l.push_back(x);
    }

    if (l.empty() || r.empty()) return f(l.empty() ? r : l, bit - 1);
    else return min(f(l, bit - 1), f(r, bit - 1)) | (1 << bit);
}
int main() {
    ios::sync_with_stdio(false); cin.tie(0);
    int n; cin >> n;
    a.clear(); a.resize(n, 0);
    for (int i = 0; i < n; i++) cin >> a[i];

    printf("%d", f(a, 30));
    return 0;
}