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: // Piyush Nagpal
  import java.util.*;
  import java.io.*;
   public class C{
       
      static int MOD=1000000007;
      static PrintWriter pw;
      static FastReader sc;
      
      static class FastReader {
          BufferedReader br;
          StringTokenizer st;
   
          public FastReader()
          {
              br = new BufferedReader(
                  new InputStreamReader(System.in));
          }
   
          String next()
          {
              while (st == null || !st.hasMoreElements()) {
                  try {
                      st = new StringTokenizer(br.readLine());
                  }
                  catch (IOException e) {
                      e.printStackTrace();
                  }
              }
              return st.nextToken();
          }
   
          int nextInt() { return Integer.parseInt(next()); }
   
          long nextLong() { return Long.parseLong(next()); }
   
          double nextDouble(){return Double.parseDouble(next());}
          
          public char nextChar() throws IOException {return next().charAt(0);}
   
          String nextLine(){
              String str = "";
              try {
                  str = br.readLine();
              }
              catch (IOException e) {
                  e.printStackTrace();
              }
              return str;
          }
          public int[] intArr(int n) throws IOException {int[]in=new int[n];for(int i=0;i<n;i++)in[i]=nextInt();return in;}
          public long[] longArr(int n) throws IOException {long[]in=new long[n];for(int i=0;i<n;i++)in[i]=nextLong();return in;}
          
      }   
  
  
       public static long gcd(long a,long b){if( b>a ){return gcd(b,a);}if( b==0 ){return a;} return gcd(b,a%b);}
       public static long expo( long a,long b,long M ){long result=1;while(b>0){if( b%2==1 ){result=(result*a)%M;}a=(a*a)%M;b=b/2;}return result%M;}
      public static ArrayList<Long> Sieve(int n){boolean [] arr= new boolean[n+1];Arrays.fill(arr, true);ArrayList<Long> list= new ArrayList<>();for(int i=2;i<=n;i++){if( arr[i]==true ){list.add((long)i);}for(int j=2*i;j<=n;j+=i){arr[j]=false;}}return list;}
  
      public static void printarr(int [] arr){for(int i=0;i<arr.length;i++){pw.print(arr[i]+" ");}}
      public static void printarr(long [] arr){for(int i=0;i<arr.length;i++){pw.print(arr[i]+" ");}}
      
      // int [] arr=sc.intArr(n);
      static void solve() throws Exception{
      	int n=sc.nextInt(),k=sc.nextInt();
          ArrayList<Long> list= new ArrayList<>();
          
          for(int i=0;i<n;i++){
              list.add(sc.nextLong());
          }
          long ans = Long.MIN_VALUE;
          for(long i=Math.max((n-300),0L);i<n;i++){
          	for(long j=i+1;j<n;j++){
          		ans=(Math.max(ans,(((i+1)*(j+1))-(k*(list.get((int)i)|list.get((int)j))))));
          	}
          }
          pw.println(ans);
   }
      
     public static void main(String[] args) throws Exception{
          try {
              System.setIn(new FileInputStream("input.txt"));
              System.setOut(new PrintStream(new FileOutputStream("output.txt")));
          } catch (Exception e) {
              System.err.println("Error");
          }
          sc= new FastReader();
          pw = new PrintWriter(System.out);
  
     
          int tc=1;
          tc=sc.nextInt();
          for(int i=1;i<=tc;i++) {
  //            pw.printf("Case #%d: "b, i);
              solve();
          }
         
          pw.flush();
  
      
  
      }
  
  }