You are an expert competitive programmer. You will be given a problem statement, test case constraints and example test inputs and outputs. Please reason step by step about the solution (that must respect memory and time limits), then provide a complete implementation in python3.

Your solution must read input from standard input (cin), write output to standard output (cout).
Do not include any debug prints or additional output.

Put your final solution within a single code block:
```python
<your code here>
```

Execution time limit: 1.0 seconds
Memory limit: 256.0 MB

# Problem
You are given a rooted tree consisting of $$$n$$$ vertices numbered from $$$1$$$ to $$$n$$$. The root is vertex $$$1$$$. There is also a string $$$s$$$ denoting the color of each vertex: if $$$s_i = \texttt{B}$$$, then vertex $$$i$$$ is black, and if $$$s_i = \texttt{W}$$$, then vertex $$$i$$$ is white.

A subtree of the tree is called balanced if the number of white vertices equals the number of black vertices. Count the number of balanced subtrees.

A tree is a connected undirected graph without cycles. A rooted tree is a tree with a selected vertex, which is called the root. In this problem, all trees have root $$$1$$$.

The tree is specified by an array of parents $$$a_2, \dots, a_n$$$ containing $$$n-1$$$ numbers: $$$a_i$$$ is the parent of the vertex with the number $$$i$$$ for all $$$i = 2, \dots, n$$$. The parent of a vertex $$$u$$$ is a vertex that is the next vertex on a simple path from $$$u$$$ to the root.

The subtree of a vertex $$$u$$$ is the set of all vertices that pass through $$$u$$$ on a simple path to the root. For example, in the picture below, $$$7$$$ is in the subtree of $$$3$$$ because the simple path $$$7 \to 5 \to 3 \to 1$$$ passes through $$$3$$$. Note that a vertex is included in its subtree, and the subtree of the root is the entire tree.

The picture shows the tree for $$$n=7$$$, $$$a=[1,1,2,3,3,5]$$$, and $$$s=\texttt{WBBWWBW}$$$. The subtree at the vertex $$$3$$$ is balanced.

## Input Format
The first line of input contains an integer $$$t$$$ ($$$1 \le t \le 10^4$$$) — the number of test cases.

The first line of each test case contains an integer $$$n$$$ ($$$2 \le n \le 4000$$$) — the number of vertices in the tree.

The second line of each test case contains $$$n-1$$$ integers $$$a_2, \dots, a_n$$$ ($$$1 \le a_i < i$$$) — the parents of the vertices $$$2, \dots, n$$$.

The third line of each test case contains a string $$$s$$$ of length $$$n$$$ consisting of the characters $$$\texttt{B}$$$ and $$$\texttt{W}$$$ — the coloring of the tree.

It is guaranteed that the sum of the values $$$n$$$ over all test cases does not exceed $$$2 \cdot 10^5$$$.

## Output Format
For each test case, output a single integer — the number of balanced subtrees.

## Examples
```input
3
7
1 1 2 3 3 5
WBBWWBW
2
1
BW
8
1 2 3 4 5 6 7
BWBWBWBW
```
```output
2
1
4
```

## Note
The first test case is pictured in the statement. Only the subtrees at vertices $$$2$$$ and $$$3$$$ are balanced.

In the second test case, only the subtree at vertex $$$1$$$ is balanced.

In the third test case, only the subtrees at vertices $$$1$$$, $$$3$$$, $$$5$$$, and $$$7$$$ are balanced.

Now solve the problem and return the code.