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: from math import *
  from decimal import *
  from decimal import Decimal as D
  from string import ascii_lowercase as lc
  from string import ascii_uppercase as uc
  from itertools import *
  from itertools import permutations as perm
  from itertools import product as prod
  from sys import *
  ip = input
  ra = lambda: list(map(int, input().split()))
  ri = lambda: int(input())
  rd = lambda: map(int, input().split())
  MOD = 10 ** 9 + 7
  MOD2 = 998244353
  maxn = 10 ** 6 + 10
  N = 10 ** 5 + 10
  N2 = 2 * 10 ** 5
  getcontext().prec = 20
  inf = 1 << 65
  def debug(*a, sep=' ', end='\n'):
      stderr.write(sep.join(map(str, a)) + end)
  def fp(x, p, m):
      r = 1
      while p:
          if p % 2:
              r = r * x % m
              p -= 1
          else:
              x = x * x % m
              p //= 2
      return r
  def fact(x, m):
      r = 1
      for i in range(2, x + 1):
          r = r * i % m
      return r
  def C(n, k, m):
      return fact(n, m) * fp(fact(n - k, m), m - 2, m) % m * fp(fact(k, m), m - 2, m) % m
  class SegmentTree:
      def f(self, a, b):
          return a + b
      def __init__(self, n, a):
          self.tree = [0] * (2 * n)
          self.n = n
          for i in range(n):
              self.tree[n + i] = a[i]
          for i in range(n - 1, 0, -1):
              self.tree[i] = self.f(self.tree[2 * i], self.tree[2 * i + 1])
      def q(self, l, r):
          l += self.n
          r += self.n
          res = 0
          while r > 1:
              if l % 2:
                  res = self.f(res, self.tree[l]) 
                  l += 1
              if r % 2:
                  r -= 1
                  res = self.f(res, self.tree[r])
              r //= 2
              l //= 2
          return res
      def u(self, index, value):
          index += self.n
          self.tree[index] = value
          index //= 2
          while index > 0:
              self.tree[index] = self.f(self.tree[2 * index], self.tree[2 * index + 1])
              index //= 2
  def z_function(s):
      l, r, n = 0, 0, len(s)
      z = [0] * n
      z[0] = 0
      for i in range(1, n):
          if r >= i: z[i] = min(z[i - l], r - i + 1)
          while z[i] + i < n and s[z[i]] == s[z[i] + i]: z[i] += 1
          if i + z[i] - 1 > r:
              l = i
              r = l + z[i] - 1
      return z
  def pc_pre(a):
      n = len(a)
      r = [0] * (n + 1)
      for i in range(n):
          r[i + 1] = r[i] + a[i]
      return r
  def pc_suf(a):
      n = len(a)
      r = [0] * (n + 1)
      for i in range(n - 1, -1, -1):
          r[i] = r[i + 1] + a[i]
      return r
  def bsloe(a, v):
      l, h = -1, len(a)
      while h - l > 1:
          m = (h + l) // 2
          if a[m] > v: h = m
          else: l = m
      return l
  def bsh(a, v):
      l, h = -1, len(a)
      while h - l > 1:
          m = (h + l) // 2
          if a[m] > v: h = m
          else: l = m
      return h
  def precalc_fact(n):
      global F
      F = [1] * (n + 1)
      for i in range(2, n + 1):
          F[i] = F[i - 1] * i
  def precalc_fact_mod(n, m):
      global F
      F = [1] * (n + 1)
      for i in range(2, n + 1):
          F[i] = F[i - 1] * i % m
  def test():
      a = [1, 2, 3]
      s = 'abcabcab'
      assert(C(3, 2, 5) == 3)
      assert(pc_pre(a) == [0, 1, 3, 6])
      assert(pc_suf(a) == [6, 5, 3, 0])
      assert(z_function(s) == [0, 0, 0, 5, 0, 0, 2, 0])
      assert(fp(2, 3, 5) == 3)
      assert(fact(3, 5) == 1)
      t = SegmentTree(3, a)
      assert(t.q(1, 3) == t.f(a[1], a[2]))
      t.u(0, 5)
      assert(t.q(0, 2) == t.f(5, a[1]))
      assert(bsh(a, 3) == 3)
      assert(bsloe(a, 3) == 2)
      debug("tests passed")
  test()
  ################    code goes here    ################
  def solve(n, k, a):
      m = -inf
      r = range(max(0, n - k - 10), n)
      for i in r:
          for j in range(i + 1, n):
              m = max((i + 1) * (j + 1) - k * (a[i] | a[j]), m)
      print(m)
  t, = rd()
  for _ in range(t):
      n, k = rd()
      a = ra()
      solve(n, k, a)