source_code: import java.util.*;
  
  public class Solution {
      public static void main(String[] args) {
          Scanner sc = new Scanner(System.in);
          for (int i = 0, t = sc.nextInt(); i < t; i++) {
              int n = sc.nextInt();
              LinkedList<Set<Integer>> stack = new LinkedList<>();
              for (int j = 0; j < n; j++) {
                  printStack(stack);
                  int val = sc.nextInt();
                  if (val == 1) {
                      Set<Integer> branch = new HashSet<>();
                      branch.add(val);
                      stack.push(branch);
                      continue;
                  }
                  Set<Integer> branch = stack.peek();
                  assert branch != null;
                  while (branch.contains(val) || branch.stream().max(Integer::compareTo).get() + 1 != val) {
                      stack.pop();
                      branch = stack.peek();
                  }
                  branch.add(val);
              }
              printStack(stack);
          }
      }
  
      public static void printStack(LinkedList<Set<Integer>> stack) {
          if (stack.size() == 0) {
              return;
          }
          StringBuilder sb = new StringBuilder();
          for (int i = stack.size() - 1; i >= 0; i--) {
              sb.append(stack.get(i).stream().max(Integer::compareTo).get()).append(".");
          }
          System.out.println(sb.substring(0, sb.length() - 1));
      }
  }
  