#include<iostream>
#include<algorithm>
#include<map>
#include<cmath>
#include<vector>
#include<set>
#define OmarNasr {ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0);}
using namespace std;
long long pre[200005], suf[200005],arr[2000005];
int main()
{
    OmarNasr;
    long long sum = 0,mx=0;
    int n, k,t;
    while (t--) {
        cin >> n >> k;
        for (int i = 1; i <= n; i++) {
            cin >> arr[i];
            pre[i] = arr[i] + pre[i - 1];
        }
        for (int i = n; i >= 1; i--) {
            suf[i] = arr[i] + suf[i + 1];
        }
        for (int i = 0; i <= n; i++) {
            int x = k - i;
            if (x < 0) {
                break;
            }
            if (x != i && x ^ i == k) {
                sum = pre[i] + suf[x];
                if (mx < sum) {
                    mx = sum;
                }
            }
        }
    cout << mx<<"\n";
    }
    return 0;
}