source_code: import java.util.*;
  public class CompressionAndExpansion {
      public static void main(String[] args) {
          Scanner in = new Scanner(System.in);
          int T = in.nextInt();
          for (int t = 0; t < T; t++) {
              int N = in.nextInt();
              List<Integer> list = new ArrayList<>();
              for (int i = 0; i < N; i++) {
                  int n = in.nextInt();
                  if (n == 1) {
                      list.add(n);
                  } else {
                      for (int j = list.size() - 1; j >= 0; j--) {
                          if (list.get(j) == n - 1) {
                              list.set(j, n);
                              break;
                          }
                          list.remove(j);
                      }
                  }
                  for (int j = 0; j < list.size(); j++) {
                      System.out.print(list.get(j) + (j == list.size() - 1 ? "\n" : "."));
                  }
              }
          }
      }
  }