using System;

public class Hello
{
    static void Main()
    {
        var n = int.Parse(Console.ReadLine().Trim());
        string[] line = Console.ReadLine().Trim().Split(' ');
        var a = Array.ConvertAll(line, long.Parse);
        getAns(n, a);
    }
    static void getAns(int n, long[] a)
    {
        long x;
        if (n == 1) x = a[0];
        else
        {
            x = a[0] | a[1];
            for (int i = 2; i < n; i++) x |= a[i];
        }
        var onf = new bool[60];
        for (int i = 0; i < 60; i++)
        {
            if (((x >> i) & 1) == 1) onf[i] = true;
        }
        var ans = -1L;
        for (int i = 0; i < 60; i++)
        {
            if (!onf[i]) { ans = 1L << i; break; }
        }
        if (ans == -1) ans = 1 << 60;
        Console.WriteLine(ans);
    }
}