#include <iostream>
#include <string>
#include <algorithm>
#include <vector>
#include <iomanip>
#include <cmath>
#include <stdio.h>
#include <queue>
#include <deque>
#include <cstdio>
#include <set>
#include <map>
#include <bitset>
#include <stack>
#include <cctype>
#include <fstream>
using namespace std;
int main() {
	int n;
	cin >> n;
	long long x = 0;
	for (int i = 0; i < n; i++) {
		long long a;
		cin >> a;
		x |= a;
	}
	long long t = 1;
	while (t <= x) {
		if (!(t & x)) {
			cout << t << endl;
			return 0;
		}
		t *= 2;
	}
	cout << t << endl;
	return 0;
}