import java.util.*;
public class Main{
    static int n;
    static int root;
    static Node[] nodes;
    static long res;
    public static void main(String[] args){
        Scanner input = new Scanner(System.in);
        n = input.nextInt(); root = input.nextInt();nodes = new Node[n+1];
        for(int i = 1 ; i <= n ;i++){
            nodes[i] = new Node();
            nodes[i].count = 1;
            nodes[i].sum = input.nextInt();
            nodes[i].avg = nodes[i].sum;
            res += nodes[i].sum;
        }
        for(int i = 0 ; i < n - 1; i ++){
            int a = input.nextInt();
            int b = input.nextInt();
            nodes[b].father = a;
        }
        for(int i = 1 ; i <= n - 1; i++){
            //循环n减一次，每次找到等效权值最大的点
            double max = -1;
            int node = 0;
            for(int j = 1 ; j <= n ; j++){
                if(j != root && nodes[j].avg > max){
                    max = nodes[j].avg;
                    node = j;
                }
            }
            int cur = node;
            int father = nodes[cur].father;
            //将当前节点和并到父节点
            res += nodes[father].count * nodes[cur].sum;
            nodes[father].sum += nodes[cur].sum;
            nodes[father].count += nodes[cur].count;
            nodes[father].avg = 1.0 * nodes[father].sum / nodes[father].count;
            nodes[cur].avg = -1;
            //将当前节点的子节点合并到父节点下面
            for(int j = 1 ; j <= n ; j++){
                if(nodes[j].father == cur){
                    nodes[j].father = father;
                }
            }
        }
        System.out.println(res);
    }

    static class Node{
        int father;
        int count;
        int sum;
        double avg;
    }
}