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


public class Main_yukicoder130_1 {

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        Printer pr = new Printer(System.out);

        int n = sc.nextInt();

        SortedSet<Integer> a = new TreeSet<>();
        for (int i = 0; i < n; i++) {
        	a.add(sc.nextInt());
        }

        pr.println(rec(0, 0, 0, a));

        pr.close();
        sc.close();
    }

	private static int rec(int mask, int bit, int max, SortedSet<Integer> a) {
		if (mask == 0x7fffffff) {
			return max;
		}

        int nmask = mask >>> 1 | 0x40000000;
		int nbit = ((~mask & 0x7fffffff) + 1) >>> 1;
		int to1 = (~nmask & 0x7fffffff | bit) + 1;
		int to2 = (~nmask & 0x7fffffff | bit | nbit) + 1;

		if (to1 < 0) {
			to1 = Integer.MAX_VALUE;
		}
		if (to2 < 0) {
			to2 = Integer.MAX_VALUE;
		}
        SortedSet<Integer> a1 = a.subSet(bit, to1);
        SortedSet<Integer> a2 = a.subSet(bit | nbit, to2);

		if (a1.size() == 0 && a2.size() == 0) {
			return Integer.MAX_VALUE;
		} else if (a2.size() == 0) {
			return rec(nmask, bit, max, a);
		} else if (a1.size() == 0) {
			return rec(nmask, bit | nbit, max, a);
		} else {
			return Math.min(rec(nmask, bit, max | nbit, a), rec(nmask, bit | nbit, max | nbit, a));
		}
	}

	@SuppressWarnings("unused")
	private static class Scanner {
		BufferedReader br;
		Iterator<String> it;

		Scanner (InputStream in) {
			br = new BufferedReader(new InputStreamReader(in));
		}

		String next() throws RuntimeException  {
			try {
				if (it == null || !it.hasNext()) {
					it = Arrays.asList(br.readLine().split(" ")).iterator();
				}
				return it.next();
			} catch (IOException e) {
				throw new IllegalStateException();
			}
		}

		int nextInt() throws RuntimeException {
			return Integer.parseInt(next());
		}

		long nextLong() throws RuntimeException {
			return Long.parseLong(next());
		}

		float nextFloat() throws RuntimeException {
			return Float.parseFloat(next());
		}

		double nextDouble() throws RuntimeException {
			return Double.parseDouble(next());
		}

		void close() {
			try {
				br.close();
			} catch (IOException e) {
//				throw new IllegalStateException();
			}
		}
	}

	private static class Printer extends PrintWriter {
		Printer(PrintStream out) {
			super(out);
		}
	}
}