# Pre, in and post

# Pre, in and post

A common problem in data structures is to determine the traversal of a binary tree. There are three classic ways to do it:

**Pre-order**: You must visit in sequence the root, left subtree and the right subtree.
**In-order**: You must visit in sequence the left subtree, the root and the right subtree.
**Post-order**: You must visit in sequence the left subtree, the right subtree and the root.

See the picture below:

The pre, in and post-order traversal are, respectively, ABCDEF, CBAEDF and CBEFDA. In this problem, you must compute the post-order traversal of a binary tree given its in-order and pre-order traversals.

#### Input

The input set consists of a positive number **c** ≤ **2000**, that gives the number of test cases and **c** lines, one for each test case. Each test case starts with a number **n** (**1** ≤ **n** ≤ **52**), the number of nodes in this binary tree. After, there will be two strings `S`

and _{1}`S`

that describe the pre-order and in-order traversal of the tree. The nodes of the tree are labeled with different characters in the range _{2}**a..z** and **A..Z**. The values of **n**, `S`

and _{1}`S`

are separeted by a blank space._{2}

#### Output

For each input set, you should output a line containing the post-order transversal for the current tree.

3 3 xYz Yxz 3 abc cba 6 ABCDEF CBAEDF

Yzx cba CBEFDA