import java.util.*;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        ArrayList<Integer> list = new ArrayList<>();
        for (int i = 0; i < n; i++) {
            list.add(sc.nextInt());
        }
        System.out.println(getAnswer(30, list));
    }
    
    static int getAnswer(int idx, ArrayList<Integer> list) {
        int mask = (1 << idx);
        ArrayList<Integer> on = new ArrayList<>();
        ArrayList<Integer> off = new ArrayList<>();
        for (int x : list) {
            if ((mask & x) == 0) {
                off.add(x);
            } else {
                on.add(x);
            }
        }
        if (on.size() > 0 && off.size() > 0) {
            if (idx == 0) {
                return 1;
            } else {
                return mask + Math.min(getAnswer(idx - 1, on), getAnswer(idx - 1, off));
            }
        } else if (on.size() > 0) {
            if (idx == 0) {
                return 0;
            } else {
                return getAnswer(idx - 1, on);
            }
        } else {
            if (idx == 0) {
                return 0;
            } else {
                return getAnswer(idx - 1, off);
            }
        }
    }
}