#include <bits/stdc++.h>
#define rep(i, a) for (int i = 0; i < (a); i++)
#define rep2(i, a, b) for (int i = (a); i < (b); i++)
#define repr(i, a) for (int i = (a) - 1; i >= 0; i--)
#define repr2(i, a, b) for (int i = (b) - 1; i >= (a); i--)
using namespace std;
typedef long long ll;
const ll inf = 1e9;
const ll mod = 1e9 + 7;

int N;

int dfs(int k, vector<int> A) {
	if (k < 0) return 0;
	vector<int> X, Y;
	rep (i, A.size()) {
		if (A[i] & 1 << k) {
			X.push_back(A[i]);
		} else {
			Y.push_back(A[i]);
		}
	}
	if (X.size() == 0 || Y.size() == 0) {
		return dfs(k - 1, A);
	} else {
		return min(dfs(k - 1, X), dfs(k - 1, Y)) + (1 << k);
	}
}

int main() {
    cin >> N;
    vector<int> A(N);
    rep (i, N) cin >> A[i];

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

    return 0;
}