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

#define rep(i,n) for(int i=0;i<(n);i++)
#define reps(i,f,n) for(int i=(f);i<(n);i++)


int dfs(int n, int mask, vector<int>& a, int sum) {
	if (mask == pow(2, n) - 1) return sum;


	vector<int> v;
	rep(i, n) {
		if ((mask & (1<<i)) == 0) v.push_back(i);
	}

	int ret = 0;
	reps(k, 1, v.size()) {
		int i = 0, j = k;
		ret = max(dfs(n, mask | (1 << v[i]) | (1 << v[j]), a, sum + (a[v[i]] ^ a[v[j]])), ret);
	}
	return ret;
}

int main(int argc, char const *argv[])
{
	int n; cin >> n;
	vector<int> a(n);
	rep(i, n) cin >> a[i];

	printf("%d\n", dfs(n, 0, a, 0));
	return 0;
}