Vanya walks late at night along a straight street of length l, lit by n lanterns. Consider the coordinate system with the beginning of the street corresponding to the point 0, and its end corresponding to the point l. Then the i-th lantern is at the point ai. The lantern lights all points of the street that are at the distance of at most d from it, where d is some positive number, common for all lanterns. 

Vanya wonders: what is the minimum light radius d should the lanterns have to light the whole street?

Input

The first line contains two integers n, l (1 ≤ n ≤ 1000, 1 ≤ l ≤ 109) — the number of lanterns and the length of the street respectively. 

The next line contains n integers ai (0 ≤ ai ≤ l). Multiple lanterns can be located at the same point. The lanterns may be located at the ends of the street.

Output

Print the minimum light radius d, needed to light the whole street. The answer will be considered correct if its absolute or relative error doesn't exceed 10 - 9.

Examples

Input

7 15
15 5 3 7 9 14 0


Output

2.5000000000


Input

2 5
2 5


Output

2.0000000000

Note

Consider the second sample. At d = 2 the first lantern will light the segment [0, 4] of the street, and the second lantern will light segment [3, 5]. Thus, the whole street will be lit.
//package clipse;


import java.util.*;
import java.util.function.Function;
import java.util.stream.Collectors;



import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.*;
import java.math.*;


public class C
{
	
	static StringBuilder sb;
	
	//static long dp[][];
	
	static long pre[];
	static int A[];
	static int n;
	static int cnt[];
	static int portal=0;
	
	
	static void solve()
   {
		
		int n=i();
		int l=i();
		int A[]=new int[n];
		boolean zero=false;
		boolean last=false;
		
		for(int i=0;i<n;i++) {
			A[i]=i();
			if(A[i]==0)
				zero=true;
			if(A[i]==l)
				last=true;
				
			
			
		}
		Arrays.sort(A);
		Double max=Double.MIN_VALUE;
		
		
		for(int i=0;i<n-1;i++)
		{
			max=Math.max(max,(double)(A[i+1]-A[i])/2);
		}
		//System.out.println(max+" ");
		
		if(zero==false)
		{
			//System.out.println("gya");
			max=Math.max(A[0],max);
		}
		if(last==false)
		{
			//System.out.println("gya");
			max=Math.max(Math.abs(l-A[n-1]),max);
		}
		
		
		
		System.out.println(max);
   }

	
		
		
		
	
	

	 public static void main(String[] args)
	    {
		 
		 int testcase=1;
		 		
	         sb=new StringBuilder();
	        int tmp=testcase;
	         while(testcase-->0)
	         {
	        	 
	        	 solve();
	         }
	         
	         System.out.println(sb);
	         
	    }
	 
	 
	 //*********************************Disjoint set union*************************//
	 static class dsu
	 {
		 int parent[];
		 int size[];
		 dsu(int n)
		 {
			 parent=new int[n];
			 size=new int[n];
			 Arrays.fill(size,-1);
			 for(int i=0;i<n;i++)
				 parent[i]=-1;
		 }
		 int find(int a)
		 {
			 if(parent[a]<0)
				 return a;
			 else
			 {
				 int x=find(parent[a]);
				 parent[a]=x;
				 return x;
			 }
		 }
		 void merge(int a,int b)
		 {
			 a=find(a);
			 b=find(b);
			 if(a==b)
				 return;
			 parent[b]=a;
			 size[a]+=size[b];
		 }
	 }
	 
	 
	 
//*******************************************PRIME FACTORIZE *****************************************************************************************************//
	 static TreeMap<Long,Long> prime(long n)
	 {
		 TreeMap<Long,Long>h=new TreeMap<>();
		 long num=n;
		 
		 for(int i=2;i<=Math.sqrt(num);i++)
		 {
			 if(n%i==0)
			 {
				 int nt=0;
				 while(n%i==0) {
					 n=n/i;
					 nt++;
				 }
				 h.put((long)i, (long)nt);
			 }
		 }
		 if(n!=1)
			 h.put((long)n, (long)1);
		 return h;
		 
	 }
	 
///////////////////////****************************************-----------------------------.........................>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>***********************************************	
	 
	static long [] xsort(long A[])
	{
		ArrayList<Long>l=new ArrayList<>();
		for(long a:A)
			l.add(a);
		Collections.sort(l);
		for(int i=0;i<l.size();i++)
			A[i]=l.get(i);
		
			return A;
		
		
	}
	 
	
//*************CLASS PAIR ***********************************************************************************************************************************************
	static class pair implements Comparable<pair>
    {
        long x;
        long y;

        pair(long x, long y) 
        {
            this.x = x;
            this.y = y;
        }
        
        public int compareTo(pair o)
        {
        	return (int)(y-o.y);
        	
        }
		
       
    }
    
//*************CLASS PAIR *****************************************************************************************************************************************************
	
	
	

    static class InputReader {
        private InputStream stream;
        private byte[] buf = new byte[1024];
        private int curChar;
        private int numChars;
        private SpaceCharFilter filter;

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

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

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

        public String String() {
            int c = read();
            while (isSpaceChar(c))
                c = read();
            StringBuilder res = new StringBuilder();
            do {
                res.appendCodePoint(c);
                c = read();
            } while (!isSpaceChar(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;
        }

        public String next() {
            return String();
        }

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

    static class OutputWriter {
        private final PrintWriter writer;

        public OutputWriter(OutputStream outputStream) {
            writer = new PrintWriter(new BufferedWriter(new OutputStreamWriter(outputStream)));
        }

        public OutputWriter(Writer writer) {
            this.writer = new PrintWriter(writer);
        }

        public void print(Object... objects) {
            for (int i = 0; i < objects.length; i++) {
                if (i != 0)
                    writer.print(' ');
                writer.print(objects[i]);
            }
        }

        public void printLine(Object... objects) {
            print(objects);
            writer.println();
        }

        public void close() {
            writer.close();
        }

        public void flush() {
            writer.flush();
        }
    }

    static InputReader in = new InputReader(System.in);
    static OutputWriter out = new OutputWriter(System.out);
    static int modulus = (int) 1e7;

    public static int[] sort(int[] a) {
        int n = a.length;
        ArrayList<Integer> l = new ArrayList<>();
        for (int i : a)
            l.add(i);
        Collections.sort(l);
        for (int i = 0; i < l.size(); i++)
            a[i] = l.get(i);
        return a;
    }

    public static long pow(long x, long y) {
        long res = 1;
        while (y > 0) {
            if (y % 2 != 0) {
                res = (res * x) % modulus;
                y--;

            }
            x = (x * x) % modulus;
            y = y / 2;
        }
        return res;
    }
//GCD___+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
    public static long gcd(long x, long y) {
        if (x == 0)
            return y;
        else
            return gcd(y % x, x);
    }
    //****************LOWEST COMMON MULTIPLE   *************************************************************************************************************************************

    public static long lcm(long x, long y) {
        return (x * (y / gcd(x, y)));
    }
//INPUT PATTERN******************************************************************************************************************************************************************
    public static int i() {
        return in.Int();
    }

    public static long l() {
        String s = in.String();
        return Long.parseLong(s);
    }

    public static String s() {
        return in.String();
    }

    public static int[] readArray(int n) {
        int A[] = new int[n];
        for (int i = 0; i < n; i++) {
            A[i] = i();
        }
        return A;
    }

    public static long[] readArray(long n) {
        long A[] = new long[(int) n];
        for (int i = 0; i < n; i++) {
            A[i] = l();
        }
        return A;
    }

//////////////////////////************************************INVERSE MODULO******************************************************************
static class inverse 
{
	static int N;
	static long[] factorialNumInverse;
	static long[] naturalNumInverse;
	static long[] fact;
	inverse(int n)
	{
		this.N=n;
		
		 factorialNumInverse = new long[N + 1];
		 
	    // Array to precompute inverse of 1! to N!
	     naturalNumInverse = new long[N + 1];
	 
	    // Array to store factorial of first N numbers
	     fact = new long[N + 1];
	     
	 
	}
	

// Function to precompute inverse of numbers
static void InverseofNumber(int p)
{
naturalNumInverse[0] = naturalNumInverse[1] = 1;

for(int i = 2; i <= N; i++)
    naturalNumInverse[i] = naturalNumInverse[p % i] *
            (long)(p - p / i) % p;
}

// Function to precompute inverse of factorials
static void InverseofFactorial(int p)
{
factorialNumInverse[0] = factorialNumInverse[1] = 1;

// Precompute inverse of natural numbers
for(int i = 2; i <= N; i++)
    factorialNumInverse[i] = (naturalNumInverse[i] *
            factorialNumInverse[i - 1]) % p;
}

// Function to calculate factorial of 1 to N
static void factorial(int p)
{
fact[0] = 1;

// Precompute factorials
for(int i = 1; i <= N; i++)
{
    fact[i] = (fact[i - 1] * (long)i) % p;
}
}

// Function to return nCr % p in O(1) time
static long comb(int N, int R, int p)
{

// n C r = n!*inverse(r!)*inverse((n-r)!)
long ans = ((fact[N] * factorialNumInverse[R]) %
        p * factorialNumInverse[N - R]) % p;

return ans;
}
}
//////////////////////////************************************INVERSE MODULO******************************************************************
}








	