description: Consider a sequence of integers a_1, a_2, …, a_n. In one move, you can select any element of the sequence and delete it. After an element is deleted, all elements to the right are shifted to the left by 1 position, so there are no empty spaces in the sequence. So after you make a move, the sequence's length decreases by 1. The indices of the elements after the move are recalculated.
  
  E. g. let the sequence be a=[3, 2, 2, 1, 5]. Let's select the element a_3=2 in a move. Then after the move the sequence will be equal to a=[3, 2, 1, 5], so the 3-rd element of the new sequence will be a_3=1 and the 4-th element will be a_4=5.
  
  You are given a sequence a_1, a_2, …, a_n and a number k. You need to find the minimum number of moves you have to make so that in the resulting sequence there will be at least k elements that are equal to their indices, i. e. the resulting sequence b_1, b_2, …, b_m will contain at least k indices i such that b_i = i.
  
  Input
  
  The first line contains one integer t (1 ≤ t ≤ 100) — the number of test cases. Then t test cases follow.
  
  Each test case consists of two consecutive lines. The first line contains two integers n and k (1 ≤ k ≤ n ≤ 2000). The second line contains a sequence of integers a_1, a_2, …, a_n (1 ≤ a_i ≤ n). The numbers in the sequence are not necessarily different.
  
  It is guaranteed that the sum of n over all test cases doesn't exceed 2000.
  
  Output
  
  For each test case output in a single line:
  
    * -1 if there's no desired move sequence; 
    * otherwise, the integer x (0 ≤ x ≤ n) — the minimum number of the moves to be made so that the resulting sequence will contain at least k elements that are equal to their indices. 
  
  Example
  
  Input
  
  
  4
  7 6
  1 1 2 3 4 5 6
  5 2
  5 1 3 2 3
  5 2
  5 5 5 5 4
  8 4
  1 2 3 3 2 2 5 5
  
  
  Output
  
  
  1
  2
  -1
  2
  
  Note
  
  In the first test case the sequence doesn't satisfy the desired condition, but it can be provided by deleting the first element, hence the sequence will be [1, 2, 3, 4, 5, 6] and 6 elements will be equal to their indices.
  
  In the second test case there are two ways to get the desired result in 2 moves: the first one is to delete the 1-st and the 3-rd elements so that the sequence will be [1, 2, 3] and have 3 elements equal to their indices; the second way is to delete the 2-nd and the 3-rd elements to get the sequence [5, 2, 3] with 2 desired elements.
solution: 
  def naiveSolve():
      
      
      
      return
  
  
  
  def main():
      
      t=int(input())
      allans=[]
      for _ in range(t):
          n,k=readIntArr()
          a=readIntArr()
          
          dp=[[-inf for __ in range(n+1)] for ___ in range(n)]
          # dp[idx][delete cnts] = max matches
          for i in range(n):
              for j in range(i+2): # j is the delete cnts
                  if a[i]==i-j+1: add=1
                  else: add=0
                  if i-1>=0: dp[i][j]=max(dp[i][j],dp[i-1][j]+add)
                  else: dp[i][j]=max(dp[i][j],add)
                  
                  if j>=1:
                      if i==0:
                          assert j==1
                          dp[i][j]=0
                      else:
                          dp[i][j]=max(dp[i][j],dp[i-1][j-1]) # delete this item
          ans=-1
          for delCnts in range(n+1):
              if dp[n-1][delCnts]>=k:
                  ans=delCnts
                  break
          allans.append(ans)
          
          # for row in dp:
          #     print(row)
          # for i in range(n):
          #     for j in range(n+1):
          #         print('i:{} j:{} dp:{}'.format(i,j,dp[i][j]))
          
      multiLineArrayPrint(allans)
      
      return
  
  
  import sys
  # input=sys.stdin.buffer.readlin,e #FOR READING PURE INTEGER INPUTS (space separation ok)
  input=lambda: sys.stdin.readline().rstrip("\r\n") #FOR READING STRING/TEXT INPUTS.
  
  def oneLineArrayPrint(arr):
      print(' '.join([str(x) for x in arr]))
  def multiLineArrayPrint(arr):
      print('\n'.join([str(x) for x in arr]))
  def multiLineArrayOfArraysPrint(arr):
      print('\n'.join([' '.join([str(x) for x in y]) for y in arr]))
   
  def readIntArr():
      return [int(x) for x in input().split()]
  # def readFloatArr():
  #     return [float(x) for x in input().split()]
   
  def makeArr(defaultValFactory,dimensionArr): # eg. makeArr(lambda:0,[n,m])
      dv=defaultValFactory;da=dimensionArr
      if len(da)==1:return [dv() for _ in range(da[0])]
      else:return [makeArr(dv,da[1:]) for _ in range(da[0])]
   
  def queryInteractive(l,r):
      print('? {} {}'.format(l,r))
      sys.stdout.flush()
      return int(input())
   
  def answerInteractive(x):
      print('! {}'.format(x))
      sys.stdout.flush()
   
  inf=float('inf')
  # MOD=10**9+7
  MOD=998244353
  
  from math import gcd,floor,ceil
  # from math import floor,ceil # for Python2
   
  for _abc in range(1):
      main()