> //求测试数据， 2天了，xxxxxxxxxxxxxxxxx谢
> #include<iostream>
> using namespace std;
> 
> int c[1010], pre[1010], next[1010];
> 
> double c1[1010];
> int n, r;
> int findmax(double c1[])//非r的最大节点
> {
> 	int i, th;
> 	double max;
> 	max = 0;
> 	th = 0;
> 	for(i = 1; i <= n; i++)
> 	{
> 		if(c1[i] > max && i != r)
> 		{
> 			max = c1[i];
> 			th = i;
> 		}
> 	}
> 	return th;
> }
> 
> void uni(int d, int pred)
> {
> 	int i;
> 	for(i = 1; i <= n; i++)
> 		if(pre[i] == d)
> 			pre[i] = pred;
> 	if(pred != r)
> 		c1[pred] = (c1[d] + c1[pred])/2;
> 	c1[d] = 0;
> 	for(i = pred; next[i] != 0; i = next[i]);
> 
> 	next[i] = d;
> 
> }
> 
> int main()
> {
> 	int i, d, e, sum;
> 	cin>>n>>r;
> 
> 	while(n || r)
> 	{
> 		pre[r] = r;
> 		memset(next, 0, sizeof(next));
> 		for(i = 1; i <= n; i++)
> 		{
> 			scanf("%d", &c[i]);
> 			c1[i] = c[i];
> 		}
> 		for(i = 1; i < n; i++)
> 		{
> 			scanf("%d%d", &d, &e);
> 			pre[e] = d;
> 		}
> 		for(i = 1; i < n; i++)
> 		{
> 			d = findmax(c1);
> 			uni(d, pre[d]);
> 		}
> 		sum = 0; 
> 		d = 1;
> 		for(i = r; i != 0; i = next[i])
> 		{
> 			sum += d*c[i];
> 			d++;
> 		}
> 		cout<<sum<<endl;
> 
> 		cin>>n>>r;
> 	}
> 	return 0;
> }