#include<bits/stdc++.h>
using lint=long long;
using real=long double;
void cmx(lint&x,lint y){if(x<y)x=y;}
int main(){
    std::cin.tie(nullptr);std::ios_base::sync_with_stdio(false);
    std::cout.setf(std::ios_base::fixed);std::cout.precision(15);
    lint n;std::cin>>n;
    std::vector<lint>a(n);
    for(lint&x:a)std::cin>>x;
    auto cal=[&a,n](std::vector<std::pair<lint,lint>>const&ind){
        return std::accumulate(ind.begin(),ind.end(),0ll,
            [&a](lint acc,std::pair<lint,lint>const&p){return acc+(a.at(p.first)^a.at(p.second));});
    };
    lint ans=0;
    auto dfs=[&,n,ckd=std::vector<lint>(n),ind=std::vector<std::pair<lint,lint>>()]
        (auto&&f) mutable
    {
        lint i=0,j=0;
        for(;i<n&&std::exchange(ckd.at(i),true);i++);
        if(i==n){
            cmx(ans,cal(ind));
            return;
        }
        for(;j<n;j++){
            if(std::exchange(ckd.at(j),true))continue;
            ind.emplace_back(i,j);
            f(f);
            ind.pop_back();
            ckd.at(j)=false;
        }
        ckd.at(i)=false;
    };
    dfs(dfs);
    std::cout<<ans<<'\n';
}