package yukicoder;

import java.util.*;

public class Q130 {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		ArrayList<Integer> a = new ArrayList<>();
		for (int i = 0; i < n; ++i) {
			a.add(sc.nextInt());
		}
		System.out.println(dfs(a, 30));
	}

	// Suppose that a is sorted
	static int dfs(ArrayList<Integer> a, int pos) {
		if (pos == -1)
			return 0;
		ArrayList<Integer> one = new ArrayList<>();
		ArrayList<Integer> zero = new ArrayList<>();
		for (int i = 0; i < a.size(); ++i) {
			if ((a.get(i) & (1 << pos)) > 0) {
				one.add(a.get(i));
			} else {
				zero.add(a.get(i));
			}
		}
		int ans = Integer.MAX_VALUE;// 10,11
		if (one.size() == 0) {
			ans = Math.min(ans, dfs(zero, pos - 1));
		} else if (zero.size() == 0) {
			ans = Math.min(ans, dfs(one, pos - 1));
		} else {
			ans = Math.min(ans, dfs(zero, pos - 1) + (1 << pos));
			ans = Math.min(ans, dfs(one, pos - 1) + (1 << pos));
		}
		return ans;
	}
}