#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <cmath>
using namespace std;
int f[100600]={0},n,m,ans=0,s[1000000]={0};
int dfs(int j)
{
	int i;
	for(i=1;i<=n;i++)
	{
		if(s[i]==0)
		{
			j=j^f[i];
			ans=max(j,ans);
			s[i]=1;
			dfs(j);
			s[i]=0;
		}
	}
	return 0;
}
int main(){
	freopen ("xor_equ.in","r",stdin);
	freopen ("xor_equ.out","w",stdout);
	int a,b,c,d;
	scanf("%d%d",&n,&m);
	for(a=1;a<=n;a++)
		scanf("%d",&f[a]);
	int j;
	for(a=1;a<=n;a++)
	{
		j=f[a];
		s[a]=1;
		ans=max(j,ans);
		dfs(j);
	}
	cout<<ans;
	return 0;
}