description: You have a permutation: an array a = [a_1, a_2, …, a_n] of distinct integers from 1 to n. The length of the permutation n is odd.
  
  Consider the following algorithm of sorting the permutation in increasing order.
  
  A helper procedure of the algorithm, f(i), takes a single argument i (1 ≤ i ≤ n-1) and does the following. If a_i > a_{i+1}, the values of a_i and a_{i+1} are exchanged. Otherwise, the permutation doesn't change.
  
  The algorithm consists of iterations, numbered with consecutive integers starting with 1. On the i-th iteration, the algorithm does the following: 
  
    * if i is odd, call f(1), f(3), …, f(n - 2); 
    * if i is even, call f(2), f(4), …, f(n - 1). 
  
  
  
  It can be proven that after a finite number of iterations the permutation will be sorted in increasing order.
  
  After how many iterations will this happen for the first time?
  
  Input
  
  Each test contains multiple test cases. The first line contains the number of test cases t (1 ≤ t ≤ 100). Description of the test cases follows.
  
  The first line of each test case contains a single integer n (3 ≤ n ≤ 999; n is odd) — the length of the permutation.
  
  The second line contains n distinct integers a_1, a_2, …, a_n (1 ≤ a_i ≤ n) — the permutation itself. 
  
  It is guaranteed that the sum of n over all test cases does not exceed 999.
  
  Output
  
  For each test case print the number of iterations after which the permutation will become sorted in increasing order for the first time.
  
  If the given permutation is already sorted, print 0.
  
  Example
  
  Input
  
  
  3
  3
  3 2 1
  7
  4 5 7 1 3 2 6
  5
  1 2 3 4 5
  
  
  Output
  
  
  3
  5
  0
  
  Note
  
  In the first test case, the permutation will be changing as follows: 
  
    * after the 1-st iteration: [2, 3, 1]; 
    * after the 2-nd iteration: [2, 1, 3]; 
    * after the 3-rd iteration: [1, 2, 3]. 
  
  
  
  In the second test case, the permutation will be changing as follows: 
  
    * after the 1-st iteration: [4, 5, 1, 7, 2, 3, 6]; 
    * after the 2-nd iteration: [4, 1, 5, 2, 7, 3, 6]; 
    * after the 3-rd iteration: [1, 4, 2, 5, 3, 7, 6]; 
    * after the 4-th iteration: [1, 2, 4, 3, 5, 6, 7]; 
    * after the 5-th iteration: [1, 2, 3, 4, 5, 6, 7]. 
  
  
  
  In the third test case, the permutation is already sorted and the answer is 0.
solution: import java.util.*;
  import java.lang.*;
  import java.io.*;
  
  public class Main
  {
      static long mod = (int)1e9+7;
  	public static void main (String[] args) throws java.lang.Exception
  	{
  		FastReader sc =new FastReader();
  		
  	    int t=sc.nextInt();
  	    
  	   // int t=1;
  	    
  	    while(t-->0)
  	    {
  	        int n=sc.nextInt();
  	        int  arr[] = sc.readArray(n);
  	        int count = 0;
  	        
  	        while(!isSorted(arr))
  	        {
  	            count++;
  	            if(count%2==0)
  	            {
  	                for(int i=1;i<n-1;i+=2)
  	                {
  	                    if(arr[i]>arr[i+1])
  	                    {
  	                        int temp = arr[i];
  	                        arr[i] = arr[i+1];
  	                        arr[i+1] = temp;
  	                    }
  	                }
  	            }
  	            else
  	            {
  	                for(int i=0;i<n-1;i+=2)
  	                {
  	                    if(arr[i]>arr[i+1])
  	                    {
  	                        int temp = arr[i];
  	                        arr[i] = arr[i+1];
  	                        arr[i+1] = temp;
  	                    }
  	                }
  	            }
  	        }
  	        System.out.println(count);
  	    }
  	}
  	
  	
  	
  	static 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());
          }
          
          float nextFloat()
          {
              return Float.parseFloat(next());
          }
   
          String nextLine()
          {
              String str = "";
              try {
                  str = br.readLine();
              }
              catch (IOException e) {
                  e.printStackTrace();
              }
              return str;
          }
          
          int[] readArray(int n) {
  			int[] a=new int[n];
  			for (int i=0; i<n; i++) a[i]=nextInt();
  			return a;
  		}
  		
  		long[] readArrayLong(int n) {
  			long[] a=new long[n];
  			for (int i=0; i<n; i++) a[i]=nextLong();
  			return a;
  		}
  		
      }
      
      public static int[] radixSort2(int[] a)
  	{
  		int n = a.length;
  		int[] c0 = new int[0x101];
  		int[] c1 = new int[0x101];
  		int[] c2 = new int[0x101];
  		int[] c3 = new int[0x101];
  		for(int v : a) {
  			c0[(v&0xff)+1]++;
  			c1[(v>>>8&0xff)+1]++;
  			c2[(v>>>16&0xff)+1]++;
  			c3[(v>>>24^0x80)+1]++;
  		}
  		for(int i = 0;i < 0xff;i++) {
  			c0[i+1] += c0[i];
  			c1[i+1] += c1[i];
  			c2[i+1] += c2[i];
  			c3[i+1] += c3[i];
  		}
  		int[] t = new int[n];
  		for(int v : a)t[c0[v&0xff]++] = v;
  		for(int v : t)a[c1[v>>>8&0xff]++] = v;
  		for(int v : a)t[c2[v>>>16&0xff]++] = v;
  		for(int v : t)a[c3[v>>>24^0x80]++] = v;
  		return a;
  	}
  	
  	
      
      public static HashMap<Integer, Integer> sortByValue(HashMap<Integer, Integer> hm)
      {
          // Create a list from elements of HashMap
          List<Map.Entry<Integer, Integer> > list =
                 new LinkedList<Map.Entry<Integer, Integer> >(hm.entrySet());
   
          // Sort the list
          Collections.sort(list, new Comparator<Map.Entry<Integer, Integer> >() {
              public int compare(Map.Entry<Integer, Integer> o1,
                                 Map.Entry<Integer, Integer> o2)
              {
                  return (o1.getValue()).compareTo(o2.getValue());
              }
          });
           
          // put data from sorted list to hashmap
          HashMap<Integer, Integer> temp = new LinkedHashMap<Integer, Integer>();
          for (Map.Entry<Integer, Integer> aa : list) {
              temp.put(aa.getKey(), aa.getValue());
          }
          return temp;
      }
      
      static void leftRotate(int arr[], int d, int n)
      {
          for (int i = 0; i < d; i++)
              leftRotatebyOne(arr, n);
      }
   
      static void leftRotatebyOne(int arr[], int n)
      {
          int i, temp;
          temp = arr[0];
          for (i = 0; i < n - 1; i++)
              arr[i] = arr[i + 1];
          arr[n-1] = temp;
          
      }
      
      static boolean isPalindrome(String str)
      {
   
          // Pointers pointing to the beginning
          // and the end of the string
          int i = 0, j = str.length() - 1;
   
          // While there are characters to compare
          while (i < j) {
   
              // If there is a mismatch
              if (str.charAt(i) != str.charAt(j))
                  return false;
   
              // Increment first pointer and
              // decrement the other
              i++;
              j--;
          }
   
          // Given string is a palindrome
          return true;
      }
      
      static boolean palindrome_array(char arr[], int n)
      {
          // Initialise flag to zero.
          int flag = 0;
   
          // Loop till array size n/2.
          for (int i = 0; i <= n / 2 && n != 0; i++) {
   
              // Check if first and last element are different
              // Then set flag to 1.
              if (arr[i] != arr[n - i - 1]) {
                  flag = 1;
                  break;
              }
          }
   
          // If flag is set then print Not Palindrome
          // else print Palindrome.
          if (flag == 1)
              return false;
          else
              return true;
      }
      
  	static boolean allElementsEqual(int[] arr,int n)
  	{
  	    int z=0;
  	        for(int i=0;i<n-1;i++)
  		    {
  		        if(arr[i]==arr[i+1])
  		        {
  		            z++;
  		        }
  		    }
  		    if(z==n-1)
  		    {
  		        return true;
  		    }
  		    else
  		    {
  		        return false;
  		    }
  		    
  	}
  	
  	static boolean allElementsDistinct(int[] arr,int n)
  	{
  	    int z=0;
  	        for(int i=0;i<n-1;i++)
  		    {
  		        if(arr[i]!=arr[i+1])
  		        {
  		            z++;
  		        }
  		    }
  		    if(z==n-1)
  		    {
  		        return true;
  		    }
  		    else
  		    {
  		        return false;
  		    }
  		    
  		    
  	}
  	
  	public static void reverse(int[] array)
      {
    
          // Length of the array
          int n = array.length;
    
          // Swaping the first half elements with last half
          // elements
          for (int i = 0; i < n / 2; i++) {
    
              // Storing the first half elements temporarily
              int temp = array[i];
    
              // Assigning the first half to the last half
              array[i] = array[n - i - 1];
    
              // Assigning the last half to the first half
              array[n - i - 1] = temp;
          }
      }
      
      public static void reverse_Long(long[] array)
      {
    
          // Length of the array
          int n = array.length;
    
          // Swaping the first half elements with last half
          // elements
          for (int i = 0; i < n / 2; i++) {
    
              // Storing the first half elements temporarily
              long temp = array[i];
    
              // Assigning the first half to the last half
              array[i] = array[n - i - 1];
    
              // Assigning the last half to the first half
              array[n - i - 1] = temp;
          }
      }
  	
  	static boolean isSorted(int[] a)
      {
          for (int i = 0; i < a.length - 1; i++)
          {
              if (a[i] > a[i + 1]) {
                  return false;
              }
          }
   
          return true;
      }
      
      
      
      static boolean isReverseSorted(int[] a)
      {
          for (int i = 0; i < a.length - 1; i++)
          {
              if (a[i] < a[i + 1]) {
                  return false;
              }
          }
   
          return true;
      }
      
      static int[] rearrangeEvenAndOdd(int arr[], int n)
      {
          ArrayList<Integer> list = new ArrayList<>();
  		    
  		    for(int i=0;i<n;i++)
  		    {
  		        if(arr[i]%2==0)
  		        {
  		            list.add(arr[i]);
  		        }
  		    }
  		    
  		    for(int i=0;i<n;i++)
  		    {
  		        if(arr[i]%2!=0)
  		        {
  		            list.add(arr[i]);
  		        }
  		    }
  		    int len = list.size();
  		    int[] array = list.stream().mapToInt(i->i).toArray();
  		    return array;
      }
      
      static long[] rearrangeEvenAndOddLong(long arr[], int n)
      {
          ArrayList<Long> list = new ArrayList<>();
  		    
  		    for(int i=0;i<n;i++)
  		    {
  		        if(arr[i]%2==0)
  		        {
  		            list.add(arr[i]);
  		        }
  		    }
  		    
  		    for(int i=0;i<n;i++)
  		    {
  		        if(arr[i]%2!=0)
  		        {
  		            list.add(arr[i]);
  		        }
  		    }
  		    int len = list.size();
  		    long[] array = list.stream().mapToLong(i->i).toArray();
  		    return array;
      }
  	
  	
      
      static boolean isPrime(long n)
      {
   
          // Check if number is less than
          // equal to 1
          if (n <= 1)
              return false;
   
          // Check if number is 2
          else if (n == 2)
              return true;
   
          // Check if n is a multiple of 2
          else if (n % 2 == 0)
              return false;
   
          // If not, then just check the odds
          for (long i = 3; i <= Math.sqrt(n); i += 2)
          {
              if (n % i == 0)
                  return false;
          }
          return true;
      }
      
      static int getSum(int n)
      {    
          int sum = 0;
            
          while (n != 0)
          {
              sum = sum + n % 10;
              n = n/10;
          }
        
      return sum;
      }
      
      static int gcd(int a, int b)
      {
        if (b == 0)
          return a;
        return gcd(b, a % b);
      }
       
      static long gcdLong(long a, long b)
      {
          if (b == 0)
          return a;
        return gcdLong(b, a % b);
      }
      
      static void swap(int i, int j)
      {
          int temp = i;
          i = j;
          j = temp;
      }
  	
  	static int countDigit(long n)
      {
          return (int)Math.floor(Math.log10(n) + 1);
      }
  	
  }