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: //package Codeforces.CF735;
  
  
  import java.io.BufferedReader;
  import java.io.IOException;
  import java.io.InputStreamReader;
  import java.io.PrintWriter;
  import java.util.Arrays;
  import java.util.StringTokenizer;
  
  public class B {
  
      static final long mod = (long) 1e9 + 7l;
  
      private static void solve(int t) {
          int n = fs.nextInt();
          int k = fs.nextInt();
          int[] pairs = new int[n];
          for (int i = 0; i < n; i++) {
              pairs[i] = fs.nextInt();
          }
          long ans = Integer.MIN_VALUE;
          int l = Math.max(1, n - 2 * k);
          for (int i = l; i <= n; i++) {
              for (int j = i + 1; j <= n; j++) {
                  ans = Math.max(ans, (long) 1 * i * j - (long) 1 * k * (pairs[i-1] | pairs[j-1]));
              }
          }
          System.out.println(ans);
  
      }
  
      public static void main(String[] args) {
          fs = new FastScanner();
          out = new PrintWriter(System.out);
          long s = System.currentTimeMillis();
          int t = fs.nextInt();
          for (int i = 1; i <= t; i++) solve(t);
          out.close();
  //        System.err.println( System.currentTimeMillis() - s + "ms" );
      }
  
      static boolean DEBUG = true;
      static PrintWriter out;
      static FastScanner fs;
  
      static void trace(Object... o) {
          if (!DEBUG) return;
          System.err.println(Arrays.deepToString(o));
      }
  
      static void pl(Object o) {
          out.println(o);
      }
  
      static void p(Object o) {
          out.print(o);
      }
  
      static long gcd(long a, long b) {
          return (b == 0) ? a : gcd(b, a % b);
      }
  
      static int gcd(int a, int b) {
          return (b == 0) ? a : gcd(b, a % b);
      }
  
      static void sieveOfEratosthenes(int n, int factors[]) {
          factors[1] = 1;
          for (int p = 2; p * p <= n; p++) {
              if (factors[p] == 0) {
                  factors[p] = p;
                  for (int i = p * p; i <= n; i += p)
                      factors[i] = p;
              }
          }
      }
  
      static long mul(long a, long b) {
          return a * b % mod;
      }
  
      static long fact(int x) {
          long ans = 1;
          for (int i = 2; i <= x; 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 long modInv(long x) {
          return fastPow(x, mod - 2);
      }
  
      static long nCk(int n, int k) {
          return mul(fact(n), mul(modInv(fact(k)), modInv(fact(n - k))));
      }
  
      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 nextInt() {
              return Integer.parseInt(next());
          }
  
          int[] readArray(int n) {
              int[] a = new int[n];
              for (int i = 0; i < n; i++)
                  a[i] = nextInt();
              return a;
          }
  
          long nextLong() {
              return Long.parseLong(next());
          }
      }
  }
  