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.util.InputMismatchException;
  import java.io.IOException;
  import java.io.InputStream;
  import java.util.ArrayList;
  
  /**
   * Built using CHelper plug-in
   * Actual solution is at the top
   *
   * @author dauom
   */
  public class Main {
    public static void main(String[] args) {
      InputStream inputStream = System.in;
      OutputStream outputStream = System.out;
      InputReader in = new InputReader(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 {
      public final void solve(int testNumber, InputReader in, PrintWriter out) {
        int n = in.nextInt();
        int k = in.nextInt();
        long x = in.nextLong() - 1;
        char[] s = in.nextCharArray();
  
        int[] c = compress(s, k);
        long[] next = new long[c.length];
        long[] cur = new long[c.length];
        long count = 1;
        for (int i = c.length - 1; i >= 0; i--) {
          if (c[i] > -1) {
            next[i] = count;
            if (count + count * (double) c[i] > 1e18) {
              count = (long) 1e18 + 1;
            } else {
              count += count * c[i];
            }
            cur[i] = count;
          }
        }
  
        StringBuilder sb = new StringBuilder();
        for (int i = 0; i < c.length; i++) {
          if (c[i] == -1) {
            sb.append('a');
          } else {
            for (int j = 0; j <= c[i]; j++) {
              if (next[i] * (double) j > x) break;
              if (next[i] + next[i] * j > x) {
                x -= next[i] * j;
                while (j-- > 0) {
                  sb.append('b');
                }
                break;
              }
            }
          }
        }
        out.println(sb);
      }
  
      private int[] compress(char[] s, int k) {
        ArrayList<Integer> count = new ArrayList<>();
        int last = -1;
        for (int i = 0; i < s.length; i++) {
          if (s[i] == 'a') {
            if (last != -1) {
              count.add((i - last) * k);
              last = -1;
            }
            count.add(-1);
          } else if (last == -1) {
            last = i;
          }
        }
        if (last != -1) {
          count.add((s.length - last) * k);
        }
        int[] ans = new int[count.size()];
        int idx = 0;
        for (int x : count) {
          ans[idx++] = x;
        }
        return ans;
      }
  
    }
  
    static final class InputReader {
      private final InputStream stream;
      private final byte[] buf = new byte[1 << 18];
      private int curChar;
      private int numChars;
  
      public InputReader() {
        this.stream = System.in;
      }
  
      public InputReader(final InputStream stream) {
        this.stream = stream;
      }
  
      private int read() {
        if (this.numChars == -1) {
          throw new UnknownError();
        } else {
          if (this.curChar >= this.numChars) {
            this.curChar = 0;
  
            try {
              this.numChars = this.stream.read(this.buf);
            } catch (IOException ex) {
              throw new InputMismatchException();
            }
  
            if (this.numChars <= 0) {
              return -1;
            }
          }
  
          return this.buf[this.curChar++];
        }
      }
  
      public final int nextInt() {
        int c;
        for (c = this.read(); isSpaceChar(c); c = this.read()) {
        }
  
        byte sgn = 1;
        if (c == 45) { // 45 == '-'
          sgn = -1;
          c = this.read();
        }
  
        int res = 0;
  
        while (c >= 48 && c <= 57) { // 48 == '0', 57 == '9'
          res *= 10;
          res += c - 48; // 48 == '0'
          c = this.read();
          if (isSpaceChar(c)) {
            return res * sgn;
          }
        }
  
        throw new InputMismatchException();
      }
  
      public final long nextLong() {
        int c;
        for (c = this.read(); isSpaceChar(c); c = this.read()) {
        }
  
        byte sgn = 1;
        if (c == 45) { // 45 == '-'
          sgn = -1;
          c = this.read();
        }
  
        long res = 0;
  
        while (c >= 48 && c <= 57) { // 48 == '0', 57 == '9'
          res *= 10L;
          res += c - 48; // 48 == '0'
          c = this.read();
          if (isSpaceChar(c)) {
            return res * sgn;
          }
        }
        throw new InputMismatchException();
      }
  
      public final String next() {
        int c;
        while (isSpaceChar(c = this.read())) {
        }
  
        StringBuilder result = new StringBuilder();
        result.appendCodePoint(c);
  
        while (!isSpaceChar(c = this.read())) {
          result.appendCodePoint(c);
        }
  
        return result.toString();
      }
  
      private static boolean isSpaceChar(final int c) {
        return c == 32 || c == 10 || c == 13 || c == 9
            || c == -1; // 32 == ' ', 10 == '\n', 13 == '\r', 9 == '\t'
      }
  
      public final char[] nextCharArray() {
        return next().toCharArray();
      }
  
    }
  }
  
  