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 java.io.OutputStream;
  import java.io.IOException;
  import java.io.InputStream;
  import java.io.PrintWriter;
  import java.io.PrintStream;
  import java.util.ArrayList;
  import java.io.InputStream;
  
  /**
   * Built using CHelper plug-in
   * Actual solution is at the top
   *
   * @author sarthakmanna
   */
  public class Main {
      public static void main(String[] args) {
          InputStream inputStream = System.in;
          OutputStream outputStream = System.out;
          FastReader in = new FastReader(inputStream);
          PrintWriter out = new PrintWriter(outputStream);
          CBAString solver = new CBAString();
          int testCount = Integer.parseInt(in.next());
          for (int i = 1; i <= testCount; i++)
              solver.solve(i, in, out);
          out.close();
      }
  
      static class CBAString {
          int N;
          long K;
          long X;
          String S;
          ArrayList<Long> starChains;
          ArrayList<String> remainingString;
  
          public void fillInputParams(FastReader in) {
              N = in.nextInt();
              K = in.nextLong();
              X = in.nextLong();
              S = in.next();
              starChains = new ArrayList<>();
              remainingString = new ArrayList<>();
              StringBuilder currString = new StringBuilder();
  
              for (int i = 0; i < S.length(); ++i) {
                  if (S.charAt(i) == '*') {
                      remainingString.add(currString.toString());
                      currString = new StringBuilder();
  
                      int j;
                      for (j = i; j < S.length() && S.charAt(j) == '*'; ++j) ;
                      starChains.add(K * (j - i));
                      i = j - 1;
                  } else {
                      currString.append(S.charAt(i));
                  }
              }
              remainingString.add(currString.toString());
          }
  
          Object solveOptimised(FastReader in) {
              ArrayList<Integer> ansLens = new ArrayList<>();
  
              for (int i = 0; i < starChains.size(); ++i) {
                  for (int j = 0; ; ++j) {
                      long count = sumRight(i + 1);
                      if (X - count < 1) {
                          ansLens.add(j);
                          break;
                      } else {
                          X -= count;
                      }
                  }
              }
  
              StringBuilder finalAns = new StringBuilder();
              int i;
              for (i = 0; i < ansLens.size(); ++i) {
                  finalAns.append(remainingString.get(i));
                  finalAns.append("b".repeat(ansLens.get(i)));
              }
              finalAns.append(remainingString.get(i));
  
              return finalAns;
          }
  
          long sumRight(int idx) {
              long ret = 1;
              double overflowCheck = ret;
              for (int i = idx; i < starChains.size(); ++i) {
                  ret *= starChains.get(i) + 1;
                  overflowCheck *= starChains.get(i) + 1;
                  if (overflowCheck > 1e18) return Long.MAX_VALUE >> 2;
              }
              return ret;
          }
  
          Object solveBrute(FastReader in) {
              return null;
          }
  
          public void solve(int testNumber, FastReader in, PrintWriter out) {
              // out.print("Case #" + testNumber + ": ");
  
              fillInputParams(in);
              Object outOptimised = solveOptimised(in);
              Object outBrute = solveBrute(in);
              if (outBrute == null) {
                  out.println(outOptimised);
              } else if (outBrute.toString().equals(outOptimised.toString())) {
                  System.out.println("OK Checked");
              } else {
                  // print input params
                  System.err.println("Actual = " + outOptimised);
                  System.err.println("Expected = " + outBrute);
                  System.err.print(7 / 0);
              }
          }
  
      }
  
      static class FastReader {
          static final int BUFSIZE = 1 << 20;
          static byte[] buf;
          static int index;
          static int total;
          static InputStream in;
  
          public FastReader(InputStream is) {
              try {
                  in = is;
                  buf = new byte[BUFSIZE];
              } catch (Exception e) {
              }
          }
  
          private int scan() {
              try {
                  if (index >= total) {
                      index = 0;
                      total = in.read(buf);
                      if (total <= 0)
                          return -1;
                  }
                  return buf[index++];
              } catch (Exception | Error e) {
                  System.err.println(e.getMessage());
                  return 13 / 0;
              }
          }
  
          public String next() {
              int c;
              for (c = scan(); c <= 32; c = scan()) ;
              StringBuilder sb = new StringBuilder();
              for (; c > 32; c = scan())
                  sb.append((char) c);
              return sb.toString();
          }
  
          public int nextInt() {
              int c, val = 0;
              for (c = scan(); c <= 32; c = scan()) ;
              boolean neg = c == '-';
              if (c == '-' || c == '+')
                  c = scan();
              for (; c >= '0' && c <= '9'; c = scan())
                  val = (val << 3) + (val << 1) + (c & 15);
              return neg ? -val : val;
          }
  
          public long nextLong() {
              int c;
              long val = 0;
              for (c = scan(); c <= 32; c = scan()) ;
              boolean neg = c == '-';
              if (c == '-' || c == '+')
                  c = scan();
              for (; c >= '0' && c <= '9'; c = scan())
                  val = (val << 3) + (val << 1) + (c & 15);
              return neg ? -val : val;
          }
  
      }
  }
  
  