Codeforces Round ＃416 (Div. 2) C. Vladik and Memorable Trip

#include<bits/stdc++.h>

using namespace std;

#define X first
#define Y second
#define eps 1e-2
#define gcd __gcd
#define pb push_back
#define PI acos(-1.0)
#define lowbit(x) (x)&(-x)
#define bug printf("!!!!!\n");
#define mem(x,y) memset(x,y,sizeof(x))

typedef long long LL;
typedef long double LD;
typedef pair<int,int> pii;
typedef unsigned long long uLL;

const int maxn = 1e5+2;
const int INF  = 1<<30;
const int mod  = 1e9+7;

int dp[maxn],n,a[maxn];
int cnt[maxn],cnt2[maxn];
int res[maxn];
void solve(){
    ;
    scanf("%d",&n);for(int i=1;i<=n;i++) scanf("%d",&a[i]),cnt[a[i]]++;
    for(int i=1;i<=n;i++){
    
        int now=0,now2=0;
        memset(cnt2,0,sizeof cnt2);
        for(int j=i;j>=1;j--){
    
            if(cnt2[a[j]]==0) now++,now2^=a[j];
            cnt2[a[j]]++;
            if(cnt2[a[j]]==cnt[a[j]]) --now;
            if(!now){
    
                res[i]=max(res[i],res[j-1]+now2);
            }
        }
        res[i]=max(res[i],res[i-1]);
    }
    cout<<res[n]<<endl;
    return;
}

int main()
{
    
// freopen("in.txt","r",stdin);
// freopen("out.txt","w",stdout);
// ios::sync_with_stdio(false);
    int t = 1;
    //scanf("%d",&t);
    while(t--){
    
    // printf("Case %d: ",cas++);
        solve();
    }
    return 0;
}