import java.io.*;
import java.util.*;

public class Main {
    public static void main(String[] args) throws Exception {
        Scanner sc = new Scanner();
        int n = sc.nextInt();
        ArrayList<Integer> list = new ArrayList<>();
        for (int i = 0; i < n; i++) {
            list.add(sc.nextInt());
        }
        System.out.println(check(29, list));
    }
    
    static int check(int idx, ArrayList<Integer> list) {
        if (idx < 0) {
            return 0;
        }
        ArrayList<Integer> ev = new ArrayList<>();
        ArrayList<Integer> odd = new ArrayList<>();
        int base = (1 << idx);
        for (int x : list) {
            if ((x & base) == 0) {
                ev.add(x);
            } else {
                odd.add(x);
            }
        }
        if (ev.size() == 0) {
            return check(idx - 1, odd);
        } else if (odd.size() == 0) {
            return check(idx - 1, ev);
        } else {
            return base + Math.min(check(idx - 1, ev), check(idx - 1, odd));
        }
    }
}
class Scanner {
    BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
    StringTokenizer st = new StringTokenizer("");
    
    public Scanner() throws Exception {
        
    }
    
    public int nextInt() throws Exception {
        return Integer.parseInt(next());
    }
    
    public long nextLong() throws Exception {
        return Long.parseLong(next());
    }
    
    public double nextDouble() throws Exception {
        return Double.parseDouble(next());
    }
    
    public String next() throws Exception {
        if (!st.hasMoreTokens()) {
            st = new StringTokenizer(br.readLine());
        }
        return st.nextToken();
    }
}