description: You are given n integers a_1, a_2, …, a_n and an integer k. Find the maximum value of i ⋅ j - k ⋅ (a_i | a_j) over all pairs (i, j) of integers with 1 ≤ i < j ≤ n. Here, | is the [bitwise OR operator](https://en.wikipedia.org/wiki/Bitwise_operation#OR).
  
  Input
  
  The first line contains a single integer t (1 ≤ t ≤ 10 000) — the number of test cases.
  
  The first line of each test case contains two integers n (2 ≤ n ≤ 10^5) and k (1 ≤ k ≤ min(n, 100)).
  
  The second line of each test case contains n integers a_1, a_2, …, a_n (0 ≤ a_i ≤ n).
  
  It is guaranteed that the sum of n over all test cases doesn't exceed 3 ⋅ 10^5.
  
  Output
  
  For each test case, print a single integer — the maximum possible value of i ⋅ j - k ⋅ (a_i | a_j).
  
  Example
  
  Input
  
  
  4
  3 3
  1 1 3
  2 2
  1 2
  4 3
  0 1 2 3
  6 6
  3 2 0 0 5 6
  
  
  Output
  
  
  -1
  -4
  3
  12
  
  Note
  
  Let f(i, j) = i ⋅ j - k ⋅ (a_i | a_j).
  
  In the first test case, 
  
    * f(1, 2) = 1 ⋅ 2 - k ⋅ (a_1 | a_2) = 2 - 3 ⋅ (1 | 1) = -1. 
    * f(1, 3) = 1 ⋅ 3 - k ⋅ (a_1 | a_3) = 3 - 3 ⋅ (1 | 3) = -6. 
    * f(2, 3) = 2 ⋅ 3 - k ⋅ (a_2 | a_3) = 6 - 3 ⋅ (1 | 3) = -3. 
  
  
  
  So the maximum is f(1, 2) = -1.
  
  In the fourth test case, the maximum is f(3, 4) = 12.
solution: import java.io.*;
  import java.util.*;
  
  import static java.lang.Math.*;
  
  public class B {
      public static void main(String[] args) throws Exception {
          PrintWriter pw = new PrintWriter(System.out);
          int test = nextInt();
          for (int t = 1; t <= test; t++) {
              int n = nextInt(), k = nextInt();
              int[] arr = new int[n + 1];
              for (int i = 1; i <= n; i++) {
                  arr[i] = nextInt();
              }
              pw.println(solve(n, k, arr));
          }
  
          pw.close();
      }
  
      static long solve(int n, long k, int[] arr) {
          int N = getLog(n);
          Pair[] pairs = new Pair[1 << N];
          Pair[] dp = new Pair[1 << N];
  
          for (int i = 0; i < pairs.length; i++) {
              pairs[i] = new Pair();
              dp[i] = new Pair();
          }
  
          for (int i = 1; i <= n; i++) {
              pairs[arr[i]].add(i);
          }
  
          for (int i = 0; i < (1 << N); ++i) {
              dp[i].add(pairs[i]);
          }
          for (int i = 0; i < N; ++i) {
              for (int mask = 0; mask < (1 << N); ++mask) {
                  if ((mask & (1 << i)) != 0) {
                      dp[mask].add(dp[mask ^ (1 << i)]);
                  }
              }
          }
  
          long res = Long.MIN_VALUE;
          for (int i = 0; i < dp.length; i++) {
              if (dp[i].size() < 2) {
                  continue;
              }
              long x = (long) dp[i].first() * dp[i].last();
              long y = k * i;
              res = max(res, x - y);
          }
  
          return res;
      }
  
      static class Pair {
          int[] arr = {0, 0};
  
          void add(int x) {
              if (arr[1] < x) {
                  arr[0] = arr[1];
                  arr[1] = x;
              } else if (arr[0] < x) {
                  arr[0] = x;
              }
          }
  
          int size() {
              if (arr[1] != 0 && arr[0] != 0) {
                  return 2;
              } else {
                  return 0;
              }
          }
  
          int first() {
              return arr[0];
          }
  
          int last() {
              return arr[1];
          }
  
          void add(Pair p) {
              for (int x : p.arr) {
                  add(x);
              }
          }
      }
  
      static void trim(TreeSet<Integer> set) {
          while (set.size() > 2) {
              set.pollFirst();
          }
      }
  
      static int getLog(int n) {
          int i = 0;
          while ((1 << i) <= n) {
              i++;
          }
          return i;
      }
  
      static void debug(Object... obj) {
          System.err.println(Arrays.deepToString(obj));
      }
  
      static int nextInt() {
          try {
              boolean in = false;
              int res = 0;
              for (; ; ) {
                  int b = System.in.read() - '0';
                  if (b >= 0) {
                      in = true;
                      res = 10 * res + b;
                  } else if (in)
                      return res;
              }
          } catch (IOException e) {
              throw new Error(e);
          }
      }
  }