Problem: 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.

Solution (in JAVA):

Solution:
import java.io.BufferedReader;
import java.io.FileReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.StringTokenizer;
import java.util.Arrays;
import java.util.Random;
import java.io.FileWriter;
import java.io.PrintWriter;
/*
    Solution Created: 18:29:37 30/09/2020
    Custom Competitive programming helper.
*/
public class Main {
	public static void solve(Reader in, Writer out) {
		int t = in.nextInt();
		while(t-->0) {
			int n = in.nextInt() ,v = in.nextInt();
			int[] a = new int[n+2];
			for(int i = 1; i<=n; i++) a[i] = in.nextInt();
			a[0] = 0;
			a[n+1] = v;
			n+=2;
			double d;
			double pL = a[0], pR = a[n-1];
			double ans = 0;
			while(true) {
				double s1 = getSpeedL(pL, a);
				double s2 = getSpeedR(pR, a);
				
				int nextPos1 = nextPosL(pL, a);
				int nextPos2 = nextPosR(pR, a);
				if(nextPos1>nextPos2) break;
				double d1 = a[nextPos1]-pL;
				double d2 = pR-a[nextPos2];
				
				double t1 = d1/s1, t2 = d2/s2;
				double mT = Math.min(t1, t2);
				ans += mT;
				pL += s1*mT;
				pR-= s2*mT;
				if(nextPos1==nextPos2) break;
			}
			d = pR-pL;
			ans+= d/(getSpeedL(pL, a)+getSpeedR(pR, a));
			out.println(ans);
		}
	}
	public static double getSpeedL(double pos, int[] a) {
		int l = 0, r = a.length-1, ans = -1;
		while(l<=r) {
			int md = (l+r)/2;
			if(a[md]<=pos) {
				ans = md;
				l = md+1;
			}else r = md-1;
		}
		return ans+1;
	}
	public static double getSpeedR(double pos, int[] a) {
		int l = 0, r = a.length-1, ans = -1;
		while(l<=r) {
			int md = (l+r)/2;
			if(a[md]>=pos) {
				ans = md;
				r = md-1;
			}else l = md+1;
		}
		return a.length-ans;
	}
	public static int nextPosL(double pos, int[] a) {
		int l = 0, r = a.length-1, ans = -1;
		while(l<=r) {
			int md = (l+r)/2;
			if(a[md]>pos) {
				ans = md;
				r = md-1;
			}else l = md+1;
		}
		return ans;
	}
	public static int nextPosR(double pos, int[] a) {
		int l = 0, r = a.length-1, ans = -1;
		while(l<=r) {
			int md = (l+r)/2;
			if(a[md]<pos) {
				ans = md;
				l = md+1;
			}else r = md-1;
		}
		return ans;
	}
	public static void main(String[] args) {
		Reader in = new Reader();
		Writer out = new Writer();
		solve(in, out);
		out.exit();
	}

static class Reader {
	static BufferedReader br;
	static StringTokenizer st;
	private int charIdx = 0;
	private String s;

	public Reader() {
		this.br = new BufferedReader(new InputStreamReader(System.in));
	}
	
	public Reader(String f){
		try {
			this.br = new BufferedReader(new FileReader(f));
		} catch (IOException e) {
			e.printStackTrace();
		}
	}
	
	public int[] na(int n) {
		int[] a = new int[n];
		for (int i = 0; i < n; i++)
			a[i] = nextInt();
		return a;
	}

	public double[] nd(int n) {
		double[] a = new double[n];
		for (int i = 0; i < n; i++)
			a[i] = nextDouble();
		return a;
	}

	public char nextChar() {
		if (s == null || charIdx >= s.length()) {
			if (st == null || !st.hasMoreTokens())
				try {
					readLine();
				} catch (Exception e) {
				}
			s = st.nextToken();
			charIdx = 0;
		}
		return s.charAt(charIdx++);
	}

	public long[] nl(int n) {
		long[] a = new long[n];
		for (int i = 0; i < n; i++)
			a[i] = nextLong();
		return a;
	}

	public char[] nca() {
		return next().toCharArray();
	}

	public String[] nS(int n) {
		String[] a = new String[n];
		for (int i = 0; i < n; i++)
			a[i] = next();
		return a;
	}

	public int nextInt() {
		if (st == null || !st.hasMoreTokens())
			try {
				readLine();
			} catch (Exception e) {
			}
		return Integer.parseInt(st.nextToken());
	}

	public double nextDouble() {
		if (st == null || !st.hasMoreTokens())
			try {
				readLine();
			} catch (Exception e) {
			}
		return Double.parseDouble(st.nextToken());
	}

	public Long nextLong() {
		if (st == null || !st.hasMoreTokens())
			try {
				readLine();
			} catch (Exception e) {
			}
		return Long.parseLong(st.nextToken());
	}

	public String next() {
		if (st == null || !st.hasMoreTokens())
			try {
				readLine();
			} catch (Exception e) {
			}
		return st.nextToken();
	}

	public static void readLine() {
		try {
			st = new StringTokenizer(br.readLine());
		} catch (Exception e) {
		}
	}
}

static class Util{
		private static Random random = new Random();
		
		public static long modInverse(long a, long MOD) {
			long[] gcdE = gcdExtended(a, MOD);
			if (gcdE[0] != 1) return -1; // Inverted doesn't exist
			long x = gcdE[1];
			return (x % MOD + MOD) % MOD;
		}
		public static long[] gcdExtended(long p, long q) {
			if (q == 0) return new long[] { p, 1, 0 };
			long[] vals = gcdExtended(q, p % q);
			long tmp = vals[2];
			vals[2] = vals[1] - (p / q) * vals[2];
			vals[1] = tmp;
			return vals;
		}
		public void fac(int n) {
			
		}
		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; 
	    }
	    public static int lowerBound(int[] a, int v) {
	    	int l = 0, h = a.length;
	    	while(l<h) {
	    		int mid = (l+h)/2;
	    		if(v<=a[mid]) h = mid;
	    		else l = mid+1;
	    	}
	    	return l;
	    }
	    public static int lowerBound(long[] a, long v) {
	    	int l = 0, h = a.length;
	    	while(l<h) {
	    		int mid = (l+h)/2;
	    		if(v<=a[mid]) h = mid;
	    		else l = mid+1;
	    	}
	    	return l;
	    }
	    public static int upperBound(int[] a, int v) {
	    	int l = 0, h = a.length;
	    	while(l<h) {
	    		int mid = (l+h)/2;
	    		if(a[mid]<=v) l = mid+1;
	    		else h = mid;
	    	}
	    	return l;
	    }
	    public static int upperBound(long[] a, long v) {
	    	int l = 0, h = a.length;
	    	while(l<h) {
	    		int mid = (l+h)/2;
	    		if(a[mid]<=v) l = mid+1;
	    		else h = mid;
	    	}
	    	return l;
	    }
	    public static boolean[] getSieve(int n) {
	        boolean[] isPrime = new boolean[n+1];
	        for (int i = 2; i <= n; i++) isPrime[i] = true;
	        for (int i = 2; i*i <= n; i++) if (isPrime[i]) 
	                for (int j = i; i*j <= n; j++) isPrime[i*j] = false;
	        return isPrime;
	    }
	    public static int gcd(int a, int b) { 
	    	int tmp = 0;
	    	while(b != 0) {
	    		tmp = b;
	    		b = a%b;
	    		a = tmp;
	    	}
	    	return a;
	    }
	    public static long gcd(long a, long b) { 
	    	long tmp = 0;
	    	while(b != 0) {
	    		tmp = b;
	    		b = a%b;
	    		a = tmp;
	    	}
	    	return a;
	    }
	    public static int random(int min, int max) {
	    	return random.nextInt(max-min+1)+min;
	    }
		public static void dbg(Object... o) { 
			System.out.println(Arrays.deepToString(o)); 
		}
		public static void reverse(int[] s, int l , int r) {
			for(int i = l; i<=(l+r)/2; i++) {
				int tmp = s[i];
				s[i] = s[r+l-i];
				s[r+l-i] = tmp;
			}
	    }
		public static void reverse(int[] s) {
			reverse(s, 0, s.length-1);
	    }
		public static void reverse(long[] s, int l , int r) {
			for(int i = l; i<=(l+r)/2; i++) {
				long tmp = s[i];
				s[i] = s[r+l-i];
				s[r+l-i] = tmp;
			}
	    }
		public static void reverse(long[] s) {
			reverse(s, 0, s.length-1);
	    }
		public static void reverse(float[] s, int l , int r) {
			for(int i = l; i<=(l+r)/2; i++) {
				float tmp = s[i];
				s[i] = s[r+l-i];
				s[r+l-i] = tmp;
			}
	    }
		public static void reverse(float[] s) {
			reverse(s, 0, s.length-1);
	    }
		public static void reverse(double[] s, int l , int r) {
			for(int i = l; i<=(l+r)/2; i++) {
				double tmp = s[i];
				s[i] = s[r+l-i];
				s[r+l-i] = tmp;
			}
	    }
		public static void reverse(double[] s) {
			reverse(s, 0, s.length-1);
	    }
		public static void reverse(char[] s, int l , int r) {
			for(int i = l; i<=(l+r)/2; i++) {
				char tmp = s[i];
				s[i] = s[r+l-i];
				s[r+l-i] = tmp;
			}
	    }
		public static void reverse(char[] s) {
			reverse(s, 0, s.length-1);
	    }
		public static <T> void reverse(T[] s, int l , int r) {
			for(int i = l; i<=(l+r)/2; i++) {
				T tmp = s[i];
				s[i] = s[r+l-i];
				s[r+l-i] = tmp;
			}
	    }
		public static <T> void reverse(T[] s) {
			reverse(s, 0, s.length-1);
	    }
		public static void shuffle(int[] s) {
	        for (int i = 0; i < s.length; ++i) {
	            int j = random.nextInt(i + 1);
	            int t = s[i];
	            s[i] = s[j];
	            s[j] = t;
	        }
	    }
	    public static void shuffle(long[] s) {
	        for (int i = 0; i < s.length; ++i) {
	            int j = random.nextInt(i + 1);
	            long t = s[i];
	            s[i] = s[j];
	            s[j] = t;
	        }
	    }
	    public static void shuffle(float[] s) {
	        for (int i = 0; i < s.length; ++i) {
	            int j = random.nextInt(i + 1);
	            float t = s[i];
	            s[i] = s[j];
	            s[j] = t;
	        }
	    }
	    public static void shuffle(double[] s) {
	        for (int i = 0; i < s.length; ++i) {
	            int j = random.nextInt(i + 1);
	            double t = s[i];
	            s[i] = s[j];
	            s[j] = t;
	        }
	    }
	    public static void shuffle(char[] s) {
	        for (int i = 0; i < s.length; ++i) {
	            int j = random.nextInt(i + 1);
	            char t = s[i];
	            s[i] = s[j];
	            s[j] = t;
	        }
	    }
	    public static <T> void shuffle(T[] s) {
	        for (int i = 0; i < s.length; ++i) {
	            int j = random.nextInt(i + 1);
	            T t = s[i];
	            s[i] = s[j];
	            s[j] = t;
	        }
	    }
		public static void sortArray(int[] a) {
	        shuffle(a);
	        Arrays.sort(a);
	    }
		public static void sortArray(long[] a) {
			shuffle(a);
	        Arrays.sort(a);
	    }
		public static void sortArray(float[] a) {
			shuffle(a);
	        Arrays.sort(a);
	    }
		public static void sortArray(double[] a) {
			shuffle(a);
	        Arrays.sort(a);
	    }
		public static void sortArray(char[] a) {
			shuffle(a);
	        Arrays.sort(a);
	    }
		public static <T extends Comparable<T>> void sortArray(T[] a) {
	        Arrays.sort(a);
	    }
	}

static class Writer {
	private PrintWriter pw;
	public Writer(){
		pw = new PrintWriter(System.out);
	}
	
	public Writer(String f){
		try {
			pw = new PrintWriter(new FileWriter(f));
		} catch (IOException e) {
			e.printStackTrace();
		}
	}
	
	public void printArray(int[] a) {
		for(int i = 0; i<a.length; i++) print(a[i]+" ");
	}
	public void printlnArray(int[] a) {
		for(int i = 0; i<a.length; i++) print(a[i]+" ");
		pw.println();
	}
	public void printArray(long[] a) {
		for(int i = 0; i<a.length; i++) print(a[i]+" ");
	}
	public void printlnArray(long[] a) {
		for(int i = 0; i<a.length; i++) print(a[i]+" ");
		pw.println();
	}
	public void print(Object o) {
		pw.print(o.toString());
	}
	public void println(Object o) {
		pw.println(o.toString());
	}
	public void println() {
		pw.println();
	}
	public void flush() {
		pw.flush();
	}
	public void exit() {
		pw.close();
	}
}
}