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: // Don't place your source in a package
  
  
  import javax.swing.*;
  import java.lang.reflect.Array;
  import java.text.DecimalFormat;
  import java.util.*;
  import java.lang.*;
  import java.io.*;
  import java.math.*;
  import java.util.stream.Stream;
  
  
  
  // Please name your class Main
  public class Main {
      static FastScanner fs=new FastScanner();
      static class FastScanner {
          BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
          StringTokenizer st=new StringTokenizer("");
          public String next() {
              while (!st.hasMoreElements())
                  try {
                      st=new StringTokenizer(br.readLine());
                  } catch (IOException e) {
                      e.printStackTrace();
                  }
              return st.nextToken();
          }
          int Int() {
              return Integer.parseInt(next());
          }
  
          long Long() {
              return Long.parseLong(next());
          }
  
          String Str(){
              return next();
          }
      }
  
  
      public static void main (String[] args) throws java.lang.Exception {
          PrintWriter out = new PrintWriter(new BufferedWriter(new OutputStreamWriter(System.out)));
          //reading /writing file
          //Scanner sc=new Scanner(new File("input.txt"));
          //PrintWriter pr=new PrintWriter("output.txt");
  
  
          int T=Int();
          for(int t=0;t<T;t++){
              int n=Int();
              int k=Int();
              int A[]=Arr(n);
  
              Solution sol=new Solution(out);
              sol.solution(A,k);
          }
          out.close();
  
      }
  
  
      public static int[] Arr(int n){
          int A[]=new int[n];
          for(int i=0;i<n;i++)A[i]=Int();
          return A;
      }
      public static int Int(){
          return fs.Int();
      }
      public static long Long(){
          return fs.Long();
      }
      public static String Str(){
          return fs.Str();
      }
  
  }
  
  
  
  
  
  
  
  
  class Solution {
      PrintWriter out;
      int INF = Integer.MAX_VALUE;
      int MOD = 1000000007;
      long mod = 1000000007;
      public Solution(PrintWriter out) {
          this.out = out;
      }
  
  
  
  
      public void solution(int A[],long k) {
          // 2 * n at most
          int n =A.length;
          long res =Long.MIN_VALUE;
          int N =Integer.numberOfTrailingZeros(Integer.highestOneBit(n))+1;
          int mask[][]=new int[(1<<N)][2];
          
  
  
          for(int i = 0;i<A.length;i++){
              mask[A[i]]=combine(mask[A[i]],new int[]{i+1,0});
          }
  
          for(int i = 0;i < N; ++i) {
              for(int bit = 0; bit < (mask.length); bit++){
                  if((bit & (1<<i)) !=0){
                      mask[bit]=combine(mask[bit],mask[bit^(1<<i)]);
                  }
              }
          }
  
  
  
          for(int i=0;i<mask.length;i++){
              if(mask[i][0]>0&&mask[i][1]>0){
                  res=Math.max(res,(mask[i][0] + 0l)*mask[i][1]-k*(i));
              }
          }
          out.println(res);
      }
  
      public int[] combine(int A[],int B[]){
          int C[]=new int[]{A[0],A[1],B[0],B[1]};
          Arrays.sort(C);
          return new int[]{C[2],C[3]};
      }
  
  
  }
  
  
  
  
  
  
  
  
  