#include<cstdio>
#include<algorithm>
#include<queue>
using namespace std;
const int maxn=50005;
struct node{
  int sum;node* ch[2];
  node(){}
  node(int x){sum=x;ch[0]=ch[1]=0;}
}t[maxn*50];int tot=0;
node* newnode(int x){
  t[++tot]=node(x);return t+tot;
}
node* root[maxn];
int n;
int l[maxn],r[maxn];
int seq[maxn],a[maxn],b[maxn];
bool cmp(const int &x,const int &y){
  return a[x]<a[y];
}
//persistable weight segment tree
void Insert1(node* rt0,node* &rt,int l,int r,int x){
  rt=newnode(rt0->sum+1);
  if(l==r)return;
  int mid=(l+r)>>1;
  if(x<=mid){
    Insert1(rt0->ch[0],rt->ch[0],l,mid,x);
    rt->ch[1]=rt0->ch[1];
  }else{
    Insert1(rt0->ch[1],rt->ch[1],mid+1,r,x);
    rt->ch[0]=rt0->ch[0];
  }
}
int query(node* rt0,node* rt1,int l,int r,int ql){
  if(l==r)return rt1->sum-rt0->sum;
  int mid=(l+r)>>1;
  int ans=0;
  if(ql>mid)return query(rt0->ch[1],rt1->ch[1],mid+1,r,ql);
  return query(rt0->ch[0],rt1->ch[0],l,mid,ql)+rt1->ch[1]->sum-rt0->ch[1]->sum;
}
int binary1(int l,int r,int pos,int x){
  while(l<=r){
    int mid=(l+r)>>1;
    if(query(root[mid-1],root[pos-1],1,n,x)>=2)l=mid+1;
    else r=mid-1;
  }
  return l-1;
}
int binary2(int l,int r,int pos,int x){
  while(l<=r){
    int mid=(l+r)>>1;
    if(query(root[pos],root[mid],1,n,x)>=2)r=mid-1;
    else l=mid+1;
  }
  return r+1;
}
void init(){
  for(int i=1;i<=n;++i)seq[i]=i;
  sort(seq+1,seq+n+1,cmp);
  for(int i=1;i<=n;++i)b[seq[i]]=i;
  root[0]=t+0;root[0]->sum=0;root[0]->ch[0]=root[0]->ch[1]=t+0;
  for(int i=1;i<=n;++i)Insert1(root[i-1],root[i],1,n,b[i]);
  for(int i=1;i<=n;++i){
    l[i]=binary1(1,i-1,i,b[i]);r[i]=binary2(i+1,n,i,b[i]);
  }
}
//persistable trie
void Insert2(node* rt0,node* &rt,int x,int depth){
  rt=newnode(rt0->sum+1);
  if(depth==-1)return;
  int t=(x>>depth)&1;
  Insert2(rt0->ch[t],rt->ch[t],x,depth-1);
  rt->ch[t^1]=rt0->ch[t^1];
}
int query2(node* rt0,node *rt1,int x,int depth){
  if(depth==-1)return 0;
  int t=(x>>depth)&1;
  if(rt1->ch[t^1]->sum!=rt0->ch[t^1]->sum){
    return (1<<depth)|query2(rt0->ch[t^1],rt1->ch[t^1],x,depth-1);
  }else{
    return query2(rt0->ch[t],rt1->ch[t],x,depth-1);
  }
}
int main(){
  scanf("%d",&n);
  for(int i=1;i<=n;++i)scanf("%d",&a[i]);
  init();
  tot=0;
  for(int i=1;i<=n;++i)Insert2(root[i-1],root[i],a[i],31);
  int ans=0;
  for(int i=1;i<=n;++i){
    if(b[i]==n)continue;
    ans=max(ans,query2(root[l[i]],root[r[i]-1],a[i],31));
  }
  printf("%d\n",ans);
  return 0;
}