#include<iostream>
#include<cstdio>
#include<algorithm>
#include<cstring>
#include<cmath>
using namespace std;
long long number[10010];
long long sum[10010];
long long AX=0; 
int main()
{
	freopen("xor_equ.in","r",stdin);
	freopen("xor_equ.out","w",stdout);
	int n;
	scanf("%d",&n);
	for(int i=1;i<=n;i++)
	{
		scanf("%lld",&number[i]);
	}
	sum[1]=number[1];
	for(int i=2;i<=n;i++)
	{
		int tmp=0;
		for(int j=1;j<i;j++)
		{
			tmp=max(number[i] xor number[j],number[i] xor sum[j]);
			if(tmp>=AX)
			{
				AX=tmp;
			}
		}
		sum[i]=AX;
	}
	int ans=0;
	for(int i=1;i<=n;i++)
	{
		if(sum[i]>=ans)
		{
			ans=sum[i];
		}
	}
	printf("%d",ans);
	return 0;
}