#include<iostream>
using namespace std;
#include<algorithm>
#include<cmath>
int transform(int num1, int num2) {
    return num1 & num2; 
}
int main(){
    int N=0;
    cin>>N;
    if(N<=0){
        return 0;
    }
    int*a=new int[N];
    for(int i=0;i<N;i++){
        cin>>a[i];
    }
    sort(a,a+N);
    int maxthing=0;
    int thing=0;
    if(N>=2){
       for(int i=0;i<N;i++){
          for(int j=i+1;j<N;j++){
              thing=transform(a[i],a[j]);
          }
          if(thing>maxthing){
              maxthing=max(thing,maxthing);
        }
       } 
    }
    cout<<maxthing<<endl;
    delete[] a;
    system("pause");
    return 0;
}