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 static java.lang.Math.max;
  import static java.lang.Math.min;
  import static java.lang.Math.abs;
  import java.util.*;
  import java.io.*;
  import java.math.*;
  
  /**
   *
   * @Har_Har_Mahadev
   */
  
  /**
   * Main , Solution , Remove Public
   */
  public class B {
  
  	public static void process() throws IOException {
  
  		int n = sc.nextInt();
  		long k = sc.nextLong();
  		long arr[] = sc.readArrayLong(n);
  		long max = -INF;
  		for( int i = max(0,n-1000); i<n; i++) {
  			for(int j = i+1; j<n; j++) {
  				max = max(max,(i+1)*1L*(j+1) - k*(arr[i]|arr[j]));
  			}
  		}
  		out.println(max);
  
  	}
  
  	//=============================================================================
  	//--------------------------The End---------------------------------
  	//=============================================================================
  	private static long INF = 2000000000000000000L, M = 1000000007, MM = 998244353;
  	private static int N = 0;
  
  	private static void google(int tt) {
  		System.out.print("Case #" + (tt) + ": ");
  	}
  
  	static FastScanner sc;
  	static FastWriter out;
  
  	public static void main(String[] args) throws IOException {
  		boolean oj = true;
  		if (oj) {
  			sc = new FastScanner();
  			out = new FastWriter(System.out);
  		} else {
  			sc = new FastScanner("input.txt");
  			out = new FastWriter("output.txt");
  		}
  		long s = System.currentTimeMillis();
  		int t = 1;
  		t = sc.nextInt();
  		int TTT = 1;
  		while (t-- > 0) {
  			//			google(TTT++);
  			process();
  		}
  		out.flush();
  		//		tr(System.currentTimeMillis()-s+"ms");
  	}
  
  	private static boolean oj = System.getProperty("ONLINE_JUDGE") != null;
  
  	private static void tr(Object... o) {
  		if (!oj)
  			System.err.println(Arrays.deepToString(o));
  	}
  
  	static class Pair implements Comparable<Pair> {
  		int x, y;
  
  		Pair(int x, int y) {
  			this.x = x;
  			this.y = y;
  		}
  
  		@Override
  		public int compareTo(Pair o) {
  			return Integer.compare(this.x, o.x);
  		}
  
  		/*
  		 	@Override
  		    public boolean equals(Object o) {
  		        if (this == o) return true;
  		        if (!(o instanceof Pair)) return false;
  		        Pair key = (Pair) o;
  		        return x == key.x && y == key.y;
  		    }
  		 
  		    @Override
  		    public int hashCode() {
  		        int result = x;
  		        result = 31 * result + y;
  		        return result;
  		    }
  		*/
  	}
  
  	/////////////////////////////////////////////////////////////////////////////////////////////////////////
  
  	static int ceil(int x, int y) {
  		return (x % y == 0 ? x / y : (x / y + 1));
  	}
  
  	static long ceil(long x, long y) {
  		return (x % y == 0 ? x / y : (x / y + 1));
  	}
  
  	static long sqrt(long z) {
  		long sqz = (long) Math.sqrt(z);
  		while (sqz * 1L * sqz < z) {
  			sqz++;
  		}
  		while (sqz * 1L * sqz > z) {
  			sqz--;
  		}
  		return sqz;
  	}
  
  	static int log2(int N) {
  		int result = (int) (Math.log(N) / Math.log(2));
  		return result;
  	}
  
  	public static long gcd(long a, long b) {
  		if (a > b)
  			a = (a + b) - (b = a);
  		if (a == 0L)
  			return b;
  		return gcd(b % a, a);
  	}
  
  	public static long lcm(long a, long b) {
  		return (a * b) / gcd(a, b);
  	}
  
  	public static int lower_bound(int[] arr, int x) {
  		int low = 0, high = arr.length - 1, mid = -1;
  		int ans = -1;
  		while (low <= high) {
  			mid = (low + high) / 2;
  
  			if (arr[mid] > x) {
  				high = mid - 1;
  			} else {
  				ans = mid;
  				low = mid + 1;
  			}
  		}
  
  		return ans;
  	}
  
  	public static int upper_bound(int[] arr, int x) {
  		int low = 0, high = arr.length - 1, mid = -1;
  		int ans = arr.length;
  		while (low < high) {
  			mid = (low + high) / 2;
  
  			if (arr[mid] >= x) {
  				ans = mid;
  				high = mid - 1;
  			} else {
  				low = mid + 1;
  			}
  		}
  
  		return ans;
  	}
  
  	static void ruffleSort(int[] a) {
  		Random get = new Random();
  		for (int i = 0; i < a.length; i++) {
  			int r = get.nextInt(a.length);
  			int temp = a[i];
  			a[i] = a[r];
  			a[r] = temp;
  		}
  		Arrays.sort(a);
  	}
  
  	static void ruffleSort(long[] a) {
  		Random get = new Random();
  		for (int i = 0; i < a.length; i++) {
  			int r = get.nextInt(a.length);
  			long temp = a[i];
  			a[i] = a[r];
  			a[r] = temp;
  		}
  		Arrays.sort(a);
  	}
  
  	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];
  	}
  
  	//custom multiset (replace with HashMap if needed)
  	public static void push(TreeMap<Integer, Integer> map, int k, int v) {
  		//map[k] += v;
  		if (!map.containsKey(k))
  			map.put(k, v);
  		else
  			map.put(k, map.get(k) + v);
  	}
  
  	public static void pull(TreeMap<Integer, Integer> map, int k, int v) {
  		//assumes map[k] >= v
  		//map[k] -= v
  		int lol = map.get(k);
  		if (lol == v)
  			map.remove(k);
  		else
  			map.put(k, lol - v);
  	}
  
  	// compress Big value to Time Limit
  	public static int[] compress(int[] arr) {
  		ArrayList<Integer> ls = new ArrayList<Integer>();
  		for (int x : arr)
  			ls.add(x);
  		Collections.sort(ls);
  		HashMap<Integer, Integer> map = new HashMap<Integer, Integer>();
  		int boof = 1; //min value
  		for (int x : ls)
  			if (!map.containsKey(x))
  				map.put(x, boof++);
  		int[] brr = new int[arr.length];
  		for (int i = 0; i < arr.length; i++)
  			brr[i] = map.get(arr[i]);
  		return brr;
  	}
  
  	// Fast Writer 
  
  	public static class FastWriter {
  		private static final int BUF_SIZE = 1 << 13;
  		private final byte[] buf = new byte[BUF_SIZE];
  		private final OutputStream out;
  		private int ptr = 0;
  
  		private FastWriter() {
  			out = null;
  		}
  
  		public FastWriter(OutputStream os) {
  			this.out = os;
  		}
  
  		public FastWriter(String path) {
  			try {
  				this.out = new FileOutputStream(path);
  			} catch (FileNotFoundException e) {
  				throw new RuntimeException("FastWriter");
  			}
  		}
  
  		public FastWriter write(byte b) {
  			buf[ptr++] = b;
  			if (ptr == BUF_SIZE)
  				innerflush();
  			return this;
  		}
  
  		public FastWriter write(char c) {
  			return write((byte) c);
  		}
  
  		public FastWriter write(char[] s) {
  			for (char c : s) {
  				buf[ptr++] = (byte) c;
  				if (ptr == BUF_SIZE)
  					innerflush();
  			}
  			return this;
  		}
  
  		public FastWriter write(String s) {
  			s.chars().forEach(c -> {
  				buf[ptr++] = (byte) c;
  				if (ptr == BUF_SIZE)
  					innerflush();
  			});
  			return this;
  		}
  
  		private static int countDigits(int l) {
  			if (l >= 1000000000)
  				return 10;
  			if (l >= 100000000)
  				return 9;
  			if (l >= 10000000)
  				return 8;
  			if (l >= 1000000)
  				return 7;
  			if (l >= 100000)
  				return 6;
  			if (l >= 10000)
  				return 5;
  			if (l >= 1000)
  				return 4;
  			if (l >= 100)
  				return 3;
  			if (l >= 10)
  				return 2;
  			return 1;
  		}
  
  		public FastWriter write(int x) {
  			if (x == Integer.MIN_VALUE) {
  				return write((long) x);
  			}
  			if (ptr + 12 >= BUF_SIZE)
  				innerflush();
  			if (x < 0) {
  				write((byte) '-');
  				x = -x;
  			}
  			int d = countDigits(x);
  			for (int i = ptr + d - 1; i >= ptr; i--) {
  				buf[i] = (byte) ('0' + x % 10);
  				x /= 10;
  			}
  			ptr += d;
  			return this;
  		}
  
  		private static int countDigits(long l) {
  			if (l >= 1000000000000000000L)
  				return 19;
  			if (l >= 100000000000000000L)
  				return 18;
  			if (l >= 10000000000000000L)
  				return 17;
  			if (l >= 1000000000000000L)
  				return 16;
  			if (l >= 100000000000000L)
  				return 15;
  			if (l >= 10000000000000L)
  				return 14;
  			if (l >= 1000000000000L)
  				return 13;
  			if (l >= 100000000000L)
  				return 12;
  			if (l >= 10000000000L)
  				return 11;
  			if (l >= 1000000000L)
  				return 10;
  			if (l >= 100000000L)
  				return 9;
  			if (l >= 10000000L)
  				return 8;
  			if (l >= 1000000L)
  				return 7;
  			if (l >= 100000L)
  				return 6;
  			if (l >= 10000L)
  				return 5;
  			if (l >= 1000L)
  				return 4;
  			if (l >= 100L)
  				return 3;
  			if (l >= 10L)
  				return 2;
  			return 1;
  		}
  
  		public FastWriter write(long x) {
  			if (x == Long.MIN_VALUE) {
  				return write("" + x);
  			}
  			if (ptr + 21 >= BUF_SIZE)
  				innerflush();
  			if (x < 0) {
  				write((byte) '-');
  				x = -x;
  			}
  			int d = countDigits(x);
  			for (int i = ptr + d - 1; i >= ptr; i--) {
  				buf[i] = (byte) ('0' + x % 10);
  				x /= 10;
  			}
  			ptr += d;
  			return this;
  		}
  
  		public FastWriter write(double x, int precision) {
  			if (x < 0) {
  				write('-');
  				x = -x;
  			}
  			x += Math.pow(10, -precision) / 2;
  			//		if(x < 0){ x = 0; }
  			write((long) x).write(".");
  			x -= (long) x;
  			for (int i = 0; i < precision; i++) {
  				x *= 10;
  				write((char) ('0' + (int) x));
  				x -= (int) x;
  			}
  			return this;
  		}
  
  		public FastWriter writeln(char c) {
  			return write(c).writeln();
  		}
  
  		public FastWriter writeln(int x) {
  			return write(x).writeln();
  		}
  
  		public FastWriter writeln(long x) {
  			return write(x).writeln();
  		}
  
  		public FastWriter writeln(double x, int precision) {
  			return write(x, precision).writeln();
  		}
  
  		public FastWriter write(int... xs) {
  			boolean first = true;
  			for (int x : xs) {
  				if (!first)
  					write(' ');
  				first = false;
  				write(x);
  			}
  			return this;
  		}
  
  		public FastWriter write(long... xs) {
  			boolean first = true;
  			for (long x : xs) {
  				if (!first)
  					write(' ');
  				first = false;
  				write(x);
  			}
  			return this;
  		}
  
  		public FastWriter writeln() {
  			return write((byte) '\n');
  		}
  
  		public FastWriter writeln(int... xs) {
  			return write(xs).writeln();
  		}
  
  		public FastWriter writeln(long... xs) {
  			return write(xs).writeln();
  		}
  
  		public FastWriter writeln(char[] line) {
  			return write(line).writeln();
  		}
  
  		public FastWriter writeln(char[]... map) {
  			for (char[] line : map)
  				write(line).writeln();
  			return this;
  		}
  
  		public FastWriter writeln(String s) {
  			return write(s).writeln();
  		}
  
  		private void innerflush() {
  			try {
  				out.write(buf, 0, ptr);
  				ptr = 0;
  			} catch (IOException e) {
  				throw new RuntimeException("innerflush");
  			}
  		}
  
  		public void flush() {
  			innerflush();
  			try {
  				out.flush();
  			} catch (IOException e) {
  				throw new RuntimeException("flush");
  			}
  		}
  
  		public FastWriter print(byte b) {
  			return write(b);
  		}
  
  		public FastWriter print(char c) {
  			return write(c);
  		}
  
  		public FastWriter print(char[] s) {
  			return write(s);
  		}
  
  		public FastWriter print(String s) {
  			return write(s);
  		}
  
  		public FastWriter print(int x) {
  			return write(x);
  		}
  
  		public FastWriter print(long x) {
  			return write(x);
  		}
  
  		public FastWriter print(double x, int precision) {
  			return write(x, precision);
  		}
  
  		public FastWriter println(char c) {
  			return writeln(c);
  		}
  
  		public FastWriter println(int x) {
  			return writeln(x);
  		}
  
  		public FastWriter println(long x) {
  			return writeln(x);
  		}
  
  		public FastWriter println(double x, int precision) {
  			return writeln(x, precision);
  		}
  
  		public FastWriter print(int... xs) {
  			return write(xs);
  		}
  
  		public FastWriter print(long... xs) {
  			return write(xs);
  		}
  
  		public FastWriter println(int... xs) {
  			return writeln(xs);
  		}
  
  		public FastWriter println(long... xs) {
  			return writeln(xs);
  		}
  
  		public FastWriter println(char[] line) {
  			return writeln(line);
  		}
  
  		public FastWriter println(char[]... map) {
  			return writeln(map);
  		}
  
  		public FastWriter println(String s) {
  			return writeln(s);
  		}
  
  		public FastWriter println() {
  			return writeln();
  		}
  	}
  
  	// Fast Inputs
  	static class FastScanner {
  		//I don't understand how this works lmao
  		private int BS = 1 << 16;
  		private char NC = (char) 0;
  		private byte[] buf = new byte[BS];
  		private int bId = 0, size = 0;
  		private char c = NC;
  		private double cnt = 1;
  		private BufferedInputStream in;
  
  		public FastScanner() {
  			in = new BufferedInputStream(System.in, BS);
  		}
  
  		public FastScanner(String s) {
  			try {
  				in = new BufferedInputStream(new FileInputStream(new File(s)), BS);
  			} catch (Exception e) {
  				in = new BufferedInputStream(System.in, BS);
  			}
  		}
  
  		private char getChar() {
  			while (bId == size) {
  				try {
  					size = in.read(buf);
  				} catch (Exception e) {
  					return NC;
  				}
  				if (size == -1)
  					return NC;
  				bId = 0;
  			}
  			return (char) buf[bId++];
  		}
  
  		public int nextInt() {
  			return (int) nextLong();
  		}
  
  		public int[] readArray(int N) {
  			int[] res = new int[N];
  			for (int i = 0; i < N; i++) {
  				res[i] = (int) nextLong();
  			}
  			return res;
  		}
  
  		public long[] readArrayLong(int N) {
  			long[] res = new long[N];
  			for (int i = 0; i < N; i++) {
  				res[i] = nextLong();
  			}
  			return res;
  		}
  
  		public int[][] readArrayMatrix(int N, int M, int Index) {
  			if (Index == 0) {
  				int[][] res = new int[N][M];
  				for (int i = 0; i < N; i++) {
  					for (int j = 0; j < M; j++)
  						res[i][j] = (int) nextLong();
  				}
  				return res;
  			}
  			int[][] res = new int[N][M];
  			for (int i = 1; i <= N; i++) {
  				for (int j = 1; j <= M; j++)
  					res[i][j] = (int) nextLong();
  			}
  			return res;
  
  		}
  
  		public long[][] readArrayMatrixLong(int N, int M, int Index) {
  			if (Index == 0) {
  				long[][] res = new long[N][M];
  				for (int i = 0; i < N; i++) {
  					for (int j = 0; j < M; j++)
  						res[i][j] = nextLong();
  				}
  				return res;
  			}
  			long[][] res = new long[N][M];
  			for (int i = 1; i <= N; i++) {
  				for (int j = 1; j <= M; j++)
  					res[i][j] = nextLong();
  			}
  			return res;
  
  		}
  
  		public long nextLong() {
  			cnt = 1;
  			boolean neg = false;
  			if (c == NC)
  				c = getChar();
  			for (; (c < '0' || c > '9'); c = getChar()) {
  				if (c == '-')
  					neg = true;
  			}
  			long res = 0;
  			for (; c >= '0' && c <= '9'; c = getChar()) {
  				res = (res << 3) + (res << 1) + c - '0';
  				cnt *= 10;
  			}
  			return neg ? -res : res;
  		}
  
  		public double nextDouble() {
  			double cur = nextLong();
  			return c != '.' ? cur : cur + nextLong() / cnt;
  		}
  
  		public double[] readArrayDouble(int N) {
  			double[] res = new double[N];
  			for (int i = 0; i < N; i++) {
  				res[i] = nextDouble();
  			}
  			return res;
  		}
  
  		public String next() {
  			StringBuilder res = new StringBuilder();
  			while (c <= 32)
  				c = getChar();
  			while (c > 32) {
  				res.append(c);
  				c = getChar();
  			}
  			return res.toString();
  		}
  
  		public String nextLine() {
  			StringBuilder res = new StringBuilder();
  			while (c <= 32)
  				c = getChar();
  			while (c != '\n') {
  				res.append(c);
  				c = getChar();
  			}
  			return res.toString();
  		}
  
  		public boolean hasNext() {
  			if (c > 32)
  				return true;
  			while (true) {
  				c = getChar();
  				if (c == NC)
  					return false;
  				else if (c > 32)
  					return true;
  			}
  		}
  	}
  
  }
  