#include <stdio.h>
#include <bits/stdc++.h>
#include <atcoder/all>
using namespace atcoder;
using namespace std;
#define rep(i,n) for (int i = 0; i < (n); ++i)
#define Inf 1000000001

int main(){
	
	int n;
	cin>>n;
	
	vector<long long> a(n);
	rep(i,n)cin>>a[i];
	
	rep(i,100){
		long long ans = 1LL;
		ans <<= i;
		
		bool f = true;
		rep(j,n){
			if(a[j]&ans){
				f = false;
				break;
			}
		}
		if(f){
			cout<<ans<<endl;
			return 0;
		}
	}
	
	return 0;
}