A tree is an undirected graph that consists of $N$ nodes and $)$ edges suchConstraints

$1S{e}^{2}N$

$1A[i]{10}^{{?}^{{?}^{?}}}5$

$1$edges$[i][j]N$

Sample testcases explanation

that there is exactly one path between each pair of nodes. A walk is a traversal

in the graph, which can be expressed as a sequence of nodes. Nodes and

edges can be repeated in the walk. Thus, we can say that a walk is a path that

allows you to repeat nodes and edges.

You are given a tree of $N$ nodes. However, each node has a restriction that

allowsionte $i$ to be visited at most $A[$i$]$ times.

Your task is to find the length of the longest walk that starts in node S and

ends in $S$ Since the answer might be large, return it modulo ${10}^{{?}^{?}}9+7.$

Input Format

The first line contains an integer, $N,$ denoting the number of nodes.

The next dine contains an integer, S$,$ denoting the node that you should start

and end the walk in

Each line $i$ of the $N$ subsequent lines $($where $1iN)$ contains an integer

describing Ais

Each line iof the $N-1$ subsequent lines $($where $0i$

Please provide optimised code