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: // HOPE
  
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  import java.io.BufferedReader;
  import java.io.IOException;
  import java.io.InputStreamReader;
  import java.math.BigInteger;
  import java.util.*;
  
  public class Codeforces1 {
      static final int mod=1_000_000_007;
  
      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());
          }
  
          String nextLine() {
              String str = "";
              try {
                  str = br.readLine();
              } catch (IOException e) {
                  e.printStackTrace();
              }
              return str;
          }
      }
  
      public static void main(String[] args) {
          FastReader s = new FastReader();
          int t = s.nextInt();
          while(t-->0)
          {
              int n = s.nextInt();
              int k = s.nextInt();
              int[] a = new int[n];
  
              for(int i=0;i<n;i++)
              {
                  a[i] = s.nextInt();
              }
  
              long res = Long.MIN_VALUE;
              for(int i=n-1;i>=Math.max(0, n-200);i--)
              {
                  for(int j=i-1;j>=Math.max(0, n-200);j--)
                  {
                      long val = ((long) (i+1) *(j+1))-(k*((long) a[i]|a[j]));
                      res = Math.max(res, val);
                  }
              }
              System.out.println(res);
  
  
          }
      }
  
  
  
  
  
  
  
  
  
  
  
  
      /////////////////////////////////////////////////THE END///////////////////////////////////////////////////////////
      //////////////////////////////////////////////////////////////////////////////////////////////////////////////////
  
      public static int gcd(int x,int y)
      {
          return y==0?x:gcd(y,x%y);
      }
      public static long gcd(long x,long y)
      {
          return y==0L?x:gcd(y,x%y);
      }
  
      public static int lcm(int a, int b) {
          return (a * b) / gcd(a, b);
      }
      public static long lcm(long a, long b) {
          return (a * b) / gcd(a, b);
      }
  
      public static long pow(long a,long b)
      {
          if(b==0L)
              return 1L;
          long tmp=1;
          while(b>1L)
          {
              if((b&1L)==1)
                  tmp*=a;
              a*=a;
              b>>=1;
          }
          return (tmp*a);
      }
  
      public static long modPow(long a,long b,long mod)
      {
          if(b==0L)
              return 1L;
          long tmp=1;
          while(b>1L)
          {
              if((b&1L)==1L)
                  tmp*=a;
  
              a*=a;
              a%=mod;
              tmp%=mod;
              b>>=1;
          }
          return (tmp*a)%mod;
      }
  
      static long mul(long a, long b) {
          return a*b%mod;
      }
  
      static long fact(int n) {
          long ans=1;
          for (int i=2; i<=n; i++) ans=mul(ans, i);
          return ans;
      }
  
      static long fastPow(long base, long exp) {
          if (exp==0) return 1;
          long half=fastPow(base, exp/2);
          if (exp%2==0) return mul(half, half);
          return mul(half, mul(half, base));
      }
  
      static boolean check(int n,int d)//check for digit 7 in 504732 number
      {
          String s = n+"";
          return s.contains(d + "");
      }
      static void reverseArray(int[] a) {
          int n = a.length;
          int[] arr = new int[n];
          for (int i = 0; i < n; i++)
              arr[i] = a[n - i - 1];
          for (int i = 0; i < n; i++)
              a[i] = arr[i];
      }
  
      static void reverseArray(long[] a) {
          int n = a.length;
          long[] arr = new long[n];
          for (int i = 0; i < n; i++)
              arr[i] = a[n - i - 1];
          for (int i = 0; i < n; i++)
              a[i] = arr[i];
      }
  
      static class Pair{
          int x, y;
          Pair(int x, int y)
          {
              this.x = x;
              this.y = y;
          }
  
          @Override
          public String toString() {
              return "Pair{" +
                      "x=" + x +
                      ", y=" + y +
                      '}';
          }
      }
      static class MyCmp implements Comparator<Pair>
      {
          public int compare(Pair p1, Pair p2)
          {
             return p1.x-p2.x;
          }
      }
  }
  