description: You are given an integer k and a string s that consists only of characters 'a' (a lowercase Latin letter) and '*' (an asterisk).
  
  Each asterisk should be replaced with several (from 0 to k inclusive) lowercase Latin letters 'b'. Different asterisk can be replaced with different counts of letter 'b'.
  
  The result of the replacement is called a BA-string.
  
  Two strings a and b are different if they either have different lengths or there exists such a position i that a_i ≠ b_i.
  
  A string a is lexicographically smaller than a string b if and only if one of the following holds: 
  
    * a is a prefix of b, but a ≠ b; 
    * in the first position where a and b differ, the string a has a letter that appears earlier in the alphabet than the corresponding letter in b. 
  
  
  
  Now consider all different BA-strings and find the x-th lexicographically smallest of them.
  
  Input
  
  The first line contains a single integer t (1 ≤ t ≤ 2000) — the number of testcases.
  
  The first line of each testcase contains three integers n, k and x (1 ≤ n ≤ 2000; 0 ≤ k ≤ 2000; 1 ≤ x ≤ 10^{18}). n is the length of string s.
  
  The second line of each testcase is a string s. It consists of n characters, each of them is either 'a' (a lowercase Latin letter) or '*' (an asterisk).
  
  The sum of n over all testcases doesn't exceed 2000. For each testcase x doesn't exceed the total number of different BA-strings. String s contains at least one character 'a'.
  
  Output
  
  For each testcase, print a single string, consisting only of characters 'b' and 'a' (lowercase Latin letters) — the x-th lexicographically smallest BA-string.
  
  Example
  
  Input
  
  
  3
  2 4 3
  a*
  4 1 3
  a**a
  6 3 20
  **a***
  
  
  Output
  
  
  abb
  abba
  babbbbbbbbb
  
  Note
  
  In the first testcase of the example, BA-strings ordered lexicographically are: 
  
    1. a
    2. ab
    3. abb
    4. abbb
    5. abbbb
  
  
  
  In the second testcase of the example, BA-strings ordered lexicographically are: 
  
    1. aa
    2. aba
    3. abba
  
  
  
  Note that string "aba" is only counted once, even though there are two ways to replace asterisks with characters 'b' to get it.
solution: import sys
  from random import randint
  input = lambda : sys.stdin.readline().strip()
  intput = lambda : map(int, input().split())
  
  def toStr(new, res):
      a = []
      n = len(new)
      c = 0
      for i in range(n):
          if new[i] == 'a':
              a.append('a')
          else:
              a.append('b' * res[c])
              c += 1
      # print(a)
      return "".join(a)
  
  def solve(k,x,s):
      s += "$"
      stk = 0
      new = []
      for i, ch in enumerate(s):
          if ch == '*': stk += 1
          else:
              if i != 0 and s[i-1] != 'a':
                  new.append(stk)
                  stk = 0
          if ch == 'a':
              new.append('a')
      q = [y for y in new if y != 'a']
      if not q: return s[:-1]
      n = len(q)
      for i in range(n):
          q[i] = q[i] * k + 1
      for i in range(n-2, -1, -1):
          q[i] *= q[i+1]
      x -= 1
  
      for i in range(n-1, -1, -1):
          if q[i] > x: break
  
      res = [0] * n
      if i == n-1:
          res[i] = x
          return toStr(new, res)
  
      while i < n-1:
          b = x // q[i+1]
          x %= q[i+1]
          res[i] = b
          i += 1
      res[-1] = x
      # print(new, res)
      return toStr(new, res)
  
  def random():
      b = []
      for i in range(randint(0,50)):
          a = randint(0,1)
          x = randint(0,20)
          if a == 0:
              b.append(x * '*')
          else:
              b.append(x * 'a')
      return ''.join(b)
  
  
  def test(x, k, s):
      A = set()
      def dfs(i, curr):
          if i >= len(s):
              A.add(str(curr))
              return
          if s[i] == '*':
              for j in range(k+1):
                  q = curr + 'b'*j
                  dfs(i+1, q)
          else: dfs(i+1, curr + 'a')
      dfs(0, "")
      return sorted(A)[x-1]
  
  
  if __name__ == '__main__':
      # print( test(319, 3, '**a***aa*aa*') )
      # print( test(20, 3, '**a***'))
  
      T, = intput()
      for _ in range(T):
          n, k, x = intput()
          s = input()
          print( solve(k,x,s) )
          # s = random()
          # k = randint(0,10)
          # x = (randint(0,20))
          # print(solve(k,x,s))
  
          # print( solve() )
  