#include <cstdio>

using namespace std;

#define LBUF 300000
#define BASE 10
#define NMAX 10000

char str[LBUF];
long long m[NMAX+2];
long long dp[NMAX+2];

int main(){
	int n,np;
	long long tmp,mx;
	int i,j;

	freopen("xor_equ.in","r",stdin);
	freopen("xor_equ.out","w",stdout);

	scanf("%d",&n);
	for(i=1;i<=n;i++)
		scanf("%lld",m+i);

	for(i=1;i<=n;i++){
		mx=0;
		for(j=0;j<i;j++)
			if(dp[j]^m[i]>mx)
				mx=dp[j]^m[i];
		dp[i]=mx;
	}

	mx=0;
	for(i=1;i<=n;i++)
		if(dp[i]>mx)mx=dp[i];
	printf("%lld",mx);
	return 0;
}