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 java.io.*;
  import java.util.*;
  
  
  
  import java.math.*;
  import java.math.BigInteger;
  
  
  public final class A
  {    
  	static PrintWriter out = new PrintWriter(System.out); 
  	static StringBuilder ans=new StringBuilder();
  	static FastReader in=new FastReader();
  	static ArrayList<Pair> g[];
  	static long mod=(long)998244353,INF=Long.MAX_VALUE;
  	static boolean set[],col[]; 
  	static int par[],tot[],partial[];
  	static int D[],P[][];
  	static int dp[][],sum=0,size[];
  	static long seg[];
  	//	static node1 seg[];
  	//static pair moves[]= {new pair(-1,0),new pair(1,0), new pair(0,-1), new pair(0,1)};
  	public static void main(String args[])throws IOException
  	{				
  		int T=i();
  		outer:while(T-->0)
  		{
  
  			int N=i(); long K=i();
  			int A[]=input(N);
  			long max=Long.MIN_VALUE;
  			for(int i=0; i<N; i++)
  			{
  				for(int j=Math.max(0, i-(201)); j<i; j++)
  				{
  				long a=(long)(i+1)*(long)(j+1);
  				
  				long b=K*(A[i]|A[j]);
  				max=Math.max(max, a-b);
  				}
  			}
  			out.println(max);
  		}
  		out.println(ans);
  		out.close();
  	}
  	static int cost(int s,int A[],int B[],int K)
  	{
  		int c=0;
  		int N=A.length;
  		for(int i=0; i<N/2; i++)
  		{
  			if(B[i]==s)continue;
  			if(s>B[i])
  			{
  				//we need to add
  				int max=Math.max(K-A[i], K-A[N-i-1]);
  				if(s-B[i]<=max)c++;
  				else c+=2;
  			}
  			else
  			{
  				int max=Math.max(A[i]-1, (K-A[N-i-1])-1);
  				if(s-B[i]<=max)c++;
  				else c+=2;
  			}
  		}
  		return c;
  	}
  	static void build(int v,int tl,int tr,long A[])
  	{
  		if(tl==tr)
  		{
  			seg[v]=A[tl];
  		}
  		else
  		{
  			int tm=(tl+tr)/2;
  			build(v*2,tl,tm,A);
  			build(v*2+1,tm+1,tr,A);
  			seg[v]=Math.min(seg[v*2], seg[v*2+1]);
  		}
  	}
  	static long ask(int v,int tl,int tr,int l,int r)
  	{
  		if(l>r)return (long)(1e10);
  		if(tl==l && tr==r)
  		{
  			return seg[v];
  		}
  		int tm=(tl+tr)/2;
  		return Math.min(ask(v*2,tl,tm,l,Math.min(tm, r)), ask(v*2+1,tm+1,tr,Math.max(l,tm+1),r));
  	}
  	static int [] sub(int A[],int B[])
  	{
  		int N=A.length;
  		int f[]=new int[N];
  		for(int i=N-1; i>=0; i--)
  		{
  			if(B[i]<A[i])
  			{
  				B[i]+=26;
  				B[i-1]-=1;
  			}
  			f[i]=B[i]-A[i];
  		}
  		for(int i=0; i<N; i++)
  		{
  			if(f[i]%2!=0)f[i+1]+=26;
  			f[i]/=2;
  		}
  		return f;
  	}
  	static int[] f(int  N)
  	{
  		char X[]=in.next().toCharArray();
  		int A[]=new int[N];
  		for(int i=0; i<N; i++)A[i]=X[i]-'a';
  		return A;
  	}
  
  
  
  
  	static int max(int a ,int b,int c,int d)
  	{
  		a=Math.max(a, b);
  		c=Math.max(c,d);
  		return Math.max(a, c);
  	}
  	static int min(int a ,int b,int c,int d)
  	{
  		a=Math.min(a, b);
  		c=Math.min(c,d);
  		return Math.min(a, c);
  	}
  
  
  
  	static HashMap<Integer,Integer> Hash(int A[])
  	{
  		HashMap<Integer,Integer> mp=new HashMap<>();
  		for(int a:A)
  		{
  			int f=mp.getOrDefault(a,0)+1;
  			mp.put(a, f);
  		}
  		return mp;
  	}
  	static long mul(long a, long b)
  	{
  		return ( a %mod * 1L * b%mod )%mod;
  	}
  	static void swap(int A[],int a,int b)
  	{
  		int t=A[a];
  		A[a]=A[b];
  		A[b]=t;
  	}
  
  
  	static int find(int a)
  	{
  		if(par[a]<0)return a;
  		return par[a]=find(par[a]);
  	}
  	static void union(int a,int b)
  	{
  		a=find(a);
  		b=find(b);
  		if(a!=b)
  		{
  			par[a]+=par[b];
  			par[b]=a;
  		}
  	}
  	static boolean isSorted(int A[])
  	{
  		for(int i=1; i<A.length; i++)
  		{
  			if(A[i]<A[i-1])return false;
  		}
  		return true;
  	}
  
  	static boolean isDivisible(StringBuilder X,int i,long num)
  	{
  		long r=0;
  		for(; i<X.length(); i++)
  		{
  			r=r*10+(X.charAt(i)-'0');
  			r=r%num;
  		}
  		return r==0;
  	}    
  
  
  
  	static int lower_Bound(int A[],int low,int high, int x) 
  	{ 
  		if (low > high) 
  			if (x >= A[high]) 
  				return A[high]; 
  
  		int mid = (low + high) / 2; 
  
  		if (A[mid] == x) 
  			return A[mid]; 
  
  		if (mid > 0 && A[mid - 1] <= x && x < A[mid]) 
  			return A[mid - 1]; 
  
  		if (x < A[mid]) 
  			return lower_Bound( A, low, mid - 1, x); 
  
  		return lower_Bound(A, mid + 1, high, x); 
  	} 
  
  	static String f(String A)
  	{
  		String X="";
  		for(int i=A.length()-1; i>=0; i--)
  		{
  			int c=A.charAt(i)-'0';
  			X+=(c+1)%2;
  		}
  		return X;
  	}
  
  	static void sort(long[] a) //check for long
  	{
  		ArrayList<Long> l=new ArrayList<>();
  		for (long i:a) l.add(i);
  		Collections.sort(l);
  		for (int i=0; i<a.length; i++) a[i]=l.get(i);
  	}
  
  	static String swap(String X,int i,int j)
  	{
  		char ch[]=X.toCharArray();
  		char a=ch[i];
  		ch[i]=ch[j];
  		ch[j]=a;
  		return new String(ch);
  	}
  
  	static int sD(long n)  
  	{  
  
  		if (n % 2 == 0 )  
  			return 2;  
  
  		for (int i = 3; i * i <= n; i += 2) {  
  			if (n % i == 0 )  
  				return i;  
  		}  
  
  		return (int)n;  
  	}  
  
  	static void setGraph(int N)
  	{
  		tot=new int[N+1];
  		partial=new int[N+1];
  		D=new int[N+1];
  		P=new int[N+1][(int)(Math.log(N)+10)];
  		set=new boolean[N+1];
  		g=new ArrayList[N+1];
  		for(int i=0; i<=N; i++)
  		{
  
  			g[i]=new ArrayList<>();		
  			D[i]=Integer.MAX_VALUE;
  			//D2[i]=INF;
  		}
  	}
  
  
  
  	static  long pow(long a,long b)
  	{
  		//long mod=1000000007;
  		long pow=1;
  		long x=a;
  		while(b!=0)
  		{
  			if((b&1)!=0)pow=(pow*x)%mod;
  			x=(x*x)%mod;
  			b/=2;
  		}
  		return pow;
  	}
  
  	static long toggleBits(long x)//one's complement || Toggle bits
  	{
  		int n=(int)(Math.floor(Math.log(x)/Math.log(2)))+1;
  
  		return ((1<<n)-1)^x;
  	}
  
  	static int countBits(long a)
  	{
  		return (int)(Math.log(a)/Math.log(2)+1);
  	}
  
  	static long fact(long N)
  	{ 
  		long n=2; 
  		if(N<=1)return 1;
  		else
  		{
  			for(int i=3; i<=N; i++)n=(n*i)%mod;
  		}
  		return n;
  	}
  
  	static int kadane(int A[])
  	{
  		int lsum=A[0],gsum=A[0];
  		for(int i=1; i<A.length; i++)
  		{
  			lsum=Math.max(lsum+A[i],A[i]);
  			gsum=Math.max(gsum,lsum);
  		}
  		return gsum;
  	}
  
  	static void sort(int[] a) {
  		ArrayList<Integer> l=new ArrayList<>();
  		for (int i:a) l.add(i);
  		Collections.sort(l);
  		for (int i=0; i<a.length; i++) a[i]=l.get(i);
  	}
  
  	static boolean isPrime(long N)
  	{
  		if (N<=1)  return false; 
  		if (N<=3)  return true; 
  		if (N%2 == 0 || N%3 == 0) return false; 
  		for (int i=5; i*i<=N; i=i+6) 
  			if (N%i == 0 || N%(i+2) == 0) 
  				return false; 
  		return true; 
  	}
  	static void print(char A[])
  	{
  		for(char c:A)System.out.print(c+" ");
  		System.out.println();
  	}
  	static void print(boolean A[])
  	{
  		for(boolean c:A)System.out.print(c+" ");
  		System.out.println();
  	}
  	static void print(int A[])
  	{
  		for(int a:A)System.out.print(a+" ");
  		System.out.println();	
  	}
  	static void print(long A[])
  	{
  		for(long i:A)System.out.print(i+ " ");
  		System.out.println();
  
  	}
  	static void print(boolean A[][])
  	{
  		for(boolean a[]:A)print(a);
  	}
  	static void print(long A[][])
  	{
  		for(long a[]:A)print(a);
  	}
  	static void print(int A[][])
  	{
  		for(int a[]:A)print(a);
  	}
  	static void print(ArrayList<Integer> A)
  	{
  		for(int a:A)System.out.print(a+" ");
  		System.out.println();
  	}
  
  	static int i()
  	{
  		return in.nextInt();
  	}
  
  	static long l()
  	{
  		return in.nextLong();
  	}
  
  	static int[] input(int N){
  		int A[]=new int[N];
  		for(int i=0; i<N; i++)
  		{
  			A[i]=in.nextInt();
  		}
  		return A;
  	}
  
  	static long[] inputLong(int N)     {
  		long A[]=new long[N];
  		for(int i=0; i<A.length; i++)A[i]=in.nextLong();
  		return A;
  	}
  
  	static long GCD(long a,long b) 
  	{
  		if(b==0)
  		{
  			return a;
  		}
  		else return GCD(b,a%b );
  	}
  
  }
  class Pair implements Comparable<Pair>
  {
  	long a,b,d;
  	Pair(long a,long  b)
  	{
  		this.a=a;
  		this.b=b;
  		d=a-b;
  	}
  	public int compareTo(Pair x)
  	{
  		if(this.d>x.d)return 1;
  		if(this.d==x.d)return 0;
  		else return -1;
  	}
  }
  
  
  //Code For FastReader
  //Code For FastReader
  //Code For FastReader
  //Code For FastReader
  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;
  	}
  
  }