There is a road with length l meters. The start of the road has coordinate 0, the end of the road has coordinate l.

There are two cars, the first standing at the start of the road and the second standing at the end of the road. They will start driving simultaneously. The first car will drive from the start to the end and the second car will drive from the end to the start.

Initially, they will drive with a speed of 1 meter per second. There are n flags at different coordinates a_1, a_2, …, a_n. Each time when any of two cars drives through a flag, the speed of that car increases by 1 meter per second.

Find how long will it take for cars to meet (to reach the same coordinate). 

Input

The first line contains one integer t (1 ≤ t ≤ 10^4): the number of test cases.

The first line of each test case contains two integers n, l (1 ≤ n ≤ 10^5, 1 ≤ l ≤ 10^9): the number of flags and the length of the road.

The second line contains n integers a_1, a_2, …, a_n in the increasing order (1 ≤ a_1 < a_2 < … < a_n < l).

It is guaranteed that the sum of n among all test cases does not exceed 10^5.

Output

For each test case print a single real number: the time required for cars to meet.

Your answer will be considered correct, if its absolute or relative error does not exceed 10^{-6}. More formally, if your answer is a and jury's answer is b, your answer will be considered correct if \frac{|a-b|}{max{(1, b)}} ≤ 10^{-6}.

Example

Input


5
2 10
1 9
1 10
1
5 7
1 2 3 4 6
2 1000000000
413470354 982876160
9 478
1 10 25 33 239 445 453 468 477


Output


3.000000000000000
3.666666666666667
2.047619047619048
329737645.750000000000000
53.700000000000000

Note

In the first test case cars will meet in the coordinate 5.

The first car will be in the coordinate 1 in 1 second and after that its speed will increase by 1 and will be equal to 2 meters per second. After 2 more seconds it will be in the coordinate 5. So, it will be in the coordinate 5 in 3 seconds.

The second car will be in the coordinate 9 in 1 second and after that its speed will increase by 1 and will be equal to 2 meters per second. After 2 more seconds it will be in the coordinate 5. So, it will be in the coordinate 5 in 3 seconds.

In the second test case after 1 second the first car will be in the coordinate 1 and will have the speed equal to 2 meters per second, the second car will be in the coordinate 9 and will have the speed equal to 1 meter per second. So, they will meet after (9-1)/(2+1) = 8/3 seconds. So, the answer is equal to 1 + 8/3 = 11/3.
/*
 *
 * @Author  Ajudiya_13(Bhargav Girdharbhai Ajudiya)
 * Dhirubhai Ambani Institute of Information And Communication Technology
 *
 */


import java.util.*;
import java.io.*;
import java.lang.*;

public class Code94
{
    public static int binarySearch(double[] array, double value){
        int start = 0;
        int end = array.length-1;
        int ans = -1;
        while(start<=end){
            int mid = (start+end)/2;
            if(Math.abs(array[mid]-value)<=0.000001){
                ans = mid;
                start = mid + 1;
            }
            else if(array[mid]<value){
                ans = mid;
                start = mid + 1;
            }
            else
                end = mid - 1;
        }
        return ans;
    }

    public static int reverseBinarySearch(double[] array, double value){
        int start = array.length-1;
        int end = 0;
        int ans = -1;
        while(start>=end){
            int mid = (start+end)/2;
            if(Math.abs(array[mid]-value)<=0.000001){
                ans = mid;
                start = mid - 1;
            }
            else if(array[mid]<value){
                ans = mid;
                start = mid - 1;
            }
            else
                end = mid + 1;
        }
        return ans;
    }
    public static void main(String[] args)
    {
        InputReader in = new InputReader(System.in);
        PrintWriter pw = new PrintWriter(System.out);

        int test_case = in.nextInt();
        for(int t=0;t<test_case;t++)
        {
            int n = in.nextInt();
            double l = (double)in.nextLong();

            double[] array = new double[n+2];
            array[0] = (double)0;
            for(int i=1;i<=n;i++)
                array[i] = (double)in.nextLong();
            array[n+1] = l;

            double[] time1 = new double[n+2];
            double[] time2 = new double[n+2];

            double currentSpeed = (double)1;
            time1[0] = 0;
            for(int i=1;i<n+2;i++) {
                time1[i] = time1[i - 1] + (array[i] - array[i - 1]) / currentSpeed;
                currentSpeed++;
            }

            currentSpeed = (double)-1;
            time2[n+1] = 0;
            for(int i=n;i>=0;i--) {
                time2[i] = time2[i + 1] + (array[i] - array[i + 1]) / currentSpeed;
                currentSpeed--;
            }

            double start = 0;
            double end = Math.pow(10,9);
            double ans = 0;
            while(end-start>0.0000001){
                double mid = (start+end)/(double)2;
                int t1 = binarySearch(time1, mid);
                int t2 = reverseBinarySearch(time2, mid);

                double d1 = array[t1] + (t1+1)*(mid-time1[t1]);
                double d2 = array[t2] - ((n+2-t2)*(mid-time2[t2]));
                //System.out.println(start+ " " + end + " " + mid + " " + t1 + " " + t2 + " " + d1 + " " + d2 ) ;
                if(Math.abs(d1-d2)<=0.000002){
                    ans = mid;
                    start = mid + 0.0000001;
                }
                else if(d1>d2){
                    end = mid - 0.0000001;
                }else{
                    ans = mid;
                    start = mid + 0.0000001;
                }
            }
            pw.printf("%8.15f\n", ans);
        }
        pw.flush();
        pw.close();
    }

    static class InputReader
    {

        private final InputStream stream;
        private final byte[] buf = new byte[8192];
        private int curChar, snumChars;
        private SpaceCharFilter filter;

        public InputReader(InputStream stream)
        {
            this.stream = stream;
        }

        public int snext()
        {
            if (snumChars == -1)
                throw new InputMismatchException();
            if (curChar >= snumChars)
            {
                curChar = 0;
                try
                {
                    snumChars = stream.read(buf);
                }
                catch (IOException e)
                {
                    throw new InputMismatchException();
                }
                if (snumChars <= 0)
                    return -1;
            }
            return buf[curChar++];
        }

        public int nextInt()
        {
            int c = snext();
            while (isSpaceChar(c))
            {
                c = snext();
            }
            int sgn = 1;
            if (c == '-')
            {
                sgn = -1;
                c = snext();
            }
            int res = 0;
            do
            {
                if (c < '0' || c > '9')
                    throw new InputMismatchException();
                res *= 10;
                res += c - '0';
                c = snext();
            } while (!isSpaceChar(c));
            return res * sgn;
        }

        public long nextLong()
        {
            int c = snext();
            while (isSpaceChar(c))
            {
                c = snext();
            }
            int sgn = 1;
            if (c == '-')
            {
                sgn = -1;
                c = snext();
            }
            long res = 0;
            do
            {
                if (c < '0' || c > '9')
                    throw new InputMismatchException();
                res *= 10;
                res += c - '0';
                c = snext();
            } while (!isSpaceChar(c));
            return res * sgn;
        }

        public int[] nextIntArray(int n)
        {
            int a[] = new int[n];
            for (int i = 0; i < n; i++)
            {
                a[i] = nextInt();
            }
            return a;
        }

        public String readString()
        {
            int c = snext();
            while (isSpaceChar(c))
            {
                c = snext();
            }
            StringBuilder res = new StringBuilder();
            do
            {
                res.appendCodePoint(c);
                c = snext();
            } while (!isSpaceChar(c));
            return res.toString();
        }

        public String nextLine()
        {
            int c = snext();
            while (isSpaceChar(c))
                c = snext();
            StringBuilder res = new StringBuilder();
            do
            {
                res.appendCodePoint(c);
                c = snext();
            } while (!isEndOfLine(c));
            return res.toString();
        }

        public boolean isSpaceChar(int c)
        {
            if (filter != null)
                return filter.isSpaceChar(c);
            return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1;
        }

        private boolean isEndOfLine(int c)
        {
            return c == '\n' || c == '\r' || c == -1;
        }

        public interface SpaceCharFilter
        {
            public boolean isSpaceChar(int ch);
        }
    }

    public static long mod = 1000000007;
    public static int d;
    public static int p;
    public static int q;

    public static int[] suffle(int[] a,Random gen)
    {
        int n = a.length;
        for(int i=0;i<n;i++)
        {
            int ind = gen.nextInt(n-i)+i;
            int temp = a[ind];
            a[ind] = a[i];
            a[i] = temp;
        }
        return a;
    }

    public static void swap(int a, int b){
        int temp = a;
        a = b;
        b = temp;
    }

    public static HashSet<Integer> primeFactorization(int n)
    {
        HashSet<Integer> a =new HashSet<Integer>();
        for(int i=2;i*i<=n;i++)
        {
            while(n%i==0)
            {
                a.add(i);
                n/=i;
            }
        }
        if(n!=1)
            a.add(n);
        return a;
    }

    public static void sieve(boolean[] isPrime,int n)
    {
        for(int i=1;i<n;i++)
            isPrime[i] = true;

        isPrime[0] = false;
        isPrime[1] = false;

        for(int i=2;i*i<n;i++)
        {
            if(isPrime[i] == true)
            {
                for(int j=(2*i);j<n;j+=i)
                    isPrime[j] = false;
            }
        }
    }

    public static int GCD(int a,int b)
    {
        if(b==0)
            return a;
        else
            return GCD(b,a%b);
    }

    public static long GCD(long a,long b)
    {
        if(b==0)
            return a;
        else
            return GCD(b,a%b);
    }

    public static void extendedEuclid(int A,int B)
    {
        if(B==0)
        {
            d = A;
            p = 1 ;
            q = 0;
        }
        else
        {
            extendedEuclid(B, A%B);
            int temp = p;
            p = q;
            q = temp - (A/B)*q;
        }
    }

    public static long LCM(long a,long b)
    {
        return (a*b)/GCD(a,b);
    }

    public static int LCM(int a,int b)
    {
        return (a*b)/GCD(a,b);
    }

    public static int binaryExponentiation(int x,int n)
    {
        int result=1;
        while(n>0)
        {
            if(n % 2 ==1)
                result=result * x;
            x=x*x;
            n=n/2;
        }
        return result;
    }

    public static long binaryExponentiation(long x,long n)
    {
        long result=1;
        while(n>0)
        {
            if(n % 2 ==1)
                result=result * x;
            x=x*x;
            n=n/2;
        }
        return result;
    }

    public static int modularExponentiation(int x,int n,int M)
    {
        int result=1;
        while(n>0)
        {
            if(n % 2 ==1)
                result=(result * x)%M;
            x=(x*x)%M;
            n=n/2;
        }
        return result;
    }

    public static long modularExponentiation(long x,long n,long M)
    {
        long result=1;
        while(n>0)
        {
            if(n % 2 ==1)
                result=(result * x)%M;
            x=(x*x)%M;
            n=n/2;
        }
        return result;
    }

    public static int modInverse(int A,int M)
    {
        return modularExponentiation(A,M-2,M);
    }

    public static long modInverse(long A,long M)
    {
        return modularExponentiation(A,M-2,M);
    }

    public static boolean isPrime(int 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 class pair implements Comparable<pair>
    {
        Integer x, y;
        pair(int x,int y)
        {
            this.x=x;
            this.y=y;
        }

        public int compareTo(pair o) {
            int result = x.compareTo(o.x);
            if(result==0)
                result = y.compareTo(o.y);

            return result;
        }

        public String toString()
        {
            return x+" "+y;
        }

        public boolean equals(Object o)
        {
            if (o instanceof pair)
            {
                pair p = (pair)o;
                return (Math.abs(p.x-x)==0 && Math.abs(p.y-y)==0);
            }
            return false;
        }

        public int hashCode()
        {
            return new Long(x).hashCode()*31 + new Long(y).hashCode();
        }
    }
}