Tree Cutting (Easy Version)

Description:

Input:

The first line contains a single integer $$$n$$$ ($$$2 \le n \le 3 \cdot 10^5$$$) — the number of vertices in the tree.

The second line contains $$$n$$$ integers $$$a_1, a_2, \dots, a_n$$$ ($$$0 \le a_i \le 2$$$) — the colors of the vertices. $$$a_i = 1$$$ means that vertex $$$i$$$ is colored red, $$$a_i = 2$$$ means that vertex $$$i$$$ is colored blue and $$$a_i = 0$$$ means that vertex $$$i$$$ is uncolored.

The $$$i$$$-th of the next $$$n - 1$$$ lines contains two integers $$$v_i$$$ and $$$u_i$$$ ($$$1 \le v_i, u_i \le n$$$, $$$v_i \ne u_i$$$) — the edges of the tree. It is guaranteed that the given edges form a tree. It is guaranteed that the tree contains at least one red vertex and at least one blue vertex.

Output:

Print a single integer — the number of nice edges in the given tree.

Sample Input:

5
2 0 0 1 2
1 2
2 3
2 4
2 5

Sample Output:

1

Sample Input:

5
1 0 0 0 2
1 2
2 3
3 4
4 5

Sample Output:

4

Sample Input:

3
1 1 2
2 3
1 3

Sample Output:

0

Note:

Here is the tree from the first example:

The only nice edge is edge $$$(2, 4)$$$. Removing it makes the tree fall apart into components $$$\{4\}$$$ and $$$\{1, 2, 3, 5\}$$$. The first component only includes a red vertex and the second component includes blue vertices and uncolored vertices.

Here is the tree from the second example:

Every edge is nice in it.

Here is the tree from the third example:

Edge $$$(1, 3)$$$ splits the into components $$$\{1\}$$$ and $$$\{3, 2\}$$$, the latter one includes both red and blue vertex, thus the edge isn't nice. Edge $$$(2, 3)$$$ splits the into components $$$\{1, 3\}$$$ and $$$\{2\}$$$, the former one includes both red and blue vertex, thus the edge also isn't nice. So the answer is 0.