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: import traceback
  import os
  import sys
  from io import BytesIO, IOBase
  
  BUFSIZE = 8192
  
  class FastIO(IOBase):
      newlines = 0
  
      def __init__(self, file):
          self._fd = file.fileno()
          self.buffer = BytesIO()
          self.writable = "x" in file.mode or "r" not in file.mode
          self.write = self.buffer.write if self.writable else None
  
      def read(self):
          while True:
              b = os.read(self._fd, max(os.fstat(self._fd).st_size, BUFSIZE))
              if not b:
                  break
              ptr = self.buffer.tell()
              self.buffer.seek(0, 2), self.buffer.write(b), self.buffer.seek(ptr)
          self.newlines = 0
          return self.buffer.read()
  
      def readline(self):
          while self.newlines == 0:
              b = os.read(self._fd, max(os.fstat(self._fd).st_size, BUFSIZE))
              self.newlines = b.count(b"\n") + (not b)
              ptr = self.buffer.tell()
              self.buffer.seek(0, 2), self.buffer.write(b), self.buffer.seek(ptr)
          self.newlines -= 1
          return self.buffer.readline()
  
      def flush(self):
          if self.writable:
              os.write(self._fd, self.buffer.getvalue())
              self.buffer.truncate(0), self.buffer.seek(0)
  
  
  class IOWrapper(IOBase):
      def __init__(self, file):
          self.buffer = FastIO(file)
          self.flush = self.buffer.flush
          self.writable = self.buffer.writable
          self.write = lambda s: self.buffer.write(s.encode("ascii"))
          self.read = lambda: self.buffer.read().decode("ascii")
          self.readline = lambda: self.buffer.readline().decode("ascii")
  
  sys.stdin = IOWrapper(sys.stdin)
  # sys.stdout = IOWrapper(sys.stdout)
  input = lambda: sys.stdin.readline().rstrip("\r\n")
  
  #####################################################################
  
  import math
  from collections import defaultdict as dfd, Counter
  from functools import lru_cache
  from itertools import accumulate
  
  def geti():
      return int(input())
  
  def gets():
      return input()
  
  def getil():
      return list(map(int, input().split()))
  
  def getsl():
      return input().split()
  
  def getinps(s):
      inps = s.split()
      m = {'i': geti, 's': gets, 'il': getil, 'sl': getsl}
      if len(inps) == 1: return m[s]()
      return [m[k]() for k in inps]
  
  def get2d(nrows, ncols, n=0):
      return [[n] * ncols for r in range(nrows)]
  
  def get_acc(a):
      return list(accumulate(a))
  
  def get_ncr(n, r, mod=10**9+7):
      num = den = 1
      r = min(r, n-r)
      for i in range(r):
          num = (num * (n - i)) % mod
          den = (den * (i + 1)) % mod
      return num * pow(den, mod - 2, mod) % mod
  
  def get_nc2(n):
      return n * (n-1) // 2
      
  def get_npr(n, r):
      if n < r: return 0
      return math.factorial(n) // math.factorial(r) 
  
  def put(a):
      return ' '.join(map(str, a))
  
  # sys.stdin = open('input.txt', 'r')
  # sys.stdout = open('output.txt', 'w')
  
  inf = float('inf')
  mod = 10 ** 9 + 7
  
  
  
  
  def main():
      (N, K), a = getinps('il il')
      ans = -inf
      t = 150
      for i in range(N-1, max(N-1-t, -1), -1):
          for j in range(i-1, max(N-1-t, -1), -1):
              x = (i+1) * (j+1) - K * (a[i] | a[j])
              # print(i, j, i * j, (a[i] | a[j]), x)
              ans = max(ans, x)
      return ans
  
  
  
  
  try:
      Test = geti()
      answers = []
      for _ in range(Test):
          ans = main()
          ans = str(ans)
          answers.append(ans)
      print('\n'.join(answers))
  
  except Exception as e:
      print(e)
      traceback.print_exc()