B.cpp

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

template<typename A, typename B> ostream& operator<<(ostream &os, const pair<A, B> &p) { return os << '(' << p.first << ", " << p.second << ')'; }
template<typename T_container, typename T = typename enable_if<!is_same<T_container, string>::value, typename T_container::value_type>::type> ostream& operator<<(ostream &os, const T_container &v) { os << '{'; string sep; for (const T &x : v) os << sep << x, sep = ", "; return os << '}'; }
 
void dbg_out() { cerr << endl; }
template<typename Head, typename... Tail> void dbg_out(Head H, Tail... T) { cerr << ' ' << H; dbg_out(T...); }
#ifdef QUYNX_DEBUG
#define dbg(...) cerr << "(" << #__VA_ARGS__ << "):", dbg_out(__VA_ARGS__)
#else
#define dbg(...)
#endif

int main() {
    ios_base::sync_with_stdio(false);
#ifndef QUYNX_DEBUG 
    cin.tie(nullptr);
#endif
    int t;
    cin >> t;
    while (t--) {
        int n; int64_t k;
        cin >> n >> k;
        vector<int> arr(n+1);
        for (int i = 1; i <= n; ++i) cin >> arr[i];
        int64_t ans = -1e9;
        for (int i = max(1, n - 200); i < n; ++i) {
            for (int j = i + 1; j <= n; ++j) {
                ans = max(ans, int64_t(i) * j - k * (arr[i] | arr[j]));
            }
        }
        cout << ans << "\n";
    }
}