#include<bits/stdc++.h>
using namespace std;

const int MAX_N = 3e5+5;
const int MAX_K = 19;
int sMin[MAX_N][MAX_K];
int sMax[MAX_N][MAX_K];
int l2[MAX_N];


#ifndef OITEST
#define PRINT_VALUE(v)
#endif

int main(int argc,char* argv[]){
#ifdef OITEST
    // #define PRINT_VALUE(v){cout<<#v<<" :"<<(v)<<endl;}
    // PRINT_VALUE(argv[0])
    string fileName="perfect";
    assert(argc==2);
    string num(argv[1]);
    string inputFileName = fileName+num+".in";
    string ansFileName = fileName+num+".ans";
    auto ansFile = ifstream(ansFileName);
    auto inputFile =ifstream(inputFileName);
    int correctAns;
    ansFile>>correctAns;
    #define cin inputFile
#endif
    cin.sync_with_stdio(false);
    cin.tie(0);
    l2[0]=0;
    l2[1]=0;
    int n;
    cin>>n;
    for(int i=1;i<=n;i++){
        cin>>sMin[i][0];
        sMax[i][0]=sMin[i][0];
    }
    for(int i=2;i<=n;i++){
        l2[i]=l2[i/2]+1;
    }
    int k=l2[n]+1;
    for(int j=1;j<=k;j++){
        for(int i=1;i+(1<<j)-1<=n;i++){
            sMax[i][j]=max(sMax[i][j-1],sMax[i+(1<<(j-1))][j-1]);
            sMin[i][j]=min(sMin[i][j-1],sMin[i+(1<<(j-1))][j-1]);
        }
    }
    int ans=INT_MIN;
    for(int l=1;l<=n;l++){
        for(int r=l;r<=n;r++){
            int j=l2[r-l+1];
            int maxlr=max(sMax[l][j],sMax[r-(1<<j)+1][j]);
            int minlr=min(sMin[l][j],sMin[r-(1<<j)+1][j]);
            ans=max(ans,maxlr^minlr);
        }
    }
    cout<<ans<<endl;
#ifdef OITEST
    assert(ans==correctAns);
#endif
}