#include <bits/stdc++.h>
using namespace std;
const int N=1010;

struct Node{int fa,last,nxt,siz;double w,sw;}a[N];
priority_queue< pair<double ,int > >q;
bool vis[N];

int main()
{
    int n,rt;scanf("%d%d",&n,&rt);
    for(int i=1;i<=n;++i)
    {
        scanf("%lf",&a[i].w);
        a[i].last=i;
        a[i].sw=a[i].w;
        a[i].siz=1;
        if(i!=rt) q.push({a[i].w,i});
    }
    for(int i=1,x,y;i<n;++i) scanf("%d%d",&x,&y),a[y].fa=x;
    memset(vis,0,sizeof(vis));
    while(!q.empty())
    {
        int x=q.top().second;q.pop();
        if(vis[x]) continue;
        vis[x]=1;
        int tx=a[x].fa;while(vis[tx] && tx!=rt) tx=a[tx].fa;

        a[a[tx].last].nxt=x;
        a[tx].last=a[x].last;

        a[tx].siz+=a[x].siz;
        a[tx].sw+=a[x].sw;

        if(tx!=rt) q.push({ a[tx].sw/a[tx].siz , tx });
    }

    int ans=0;for(int i=1,x=rt;i<=n;++i,x=a[x].nxt) ans+=i*a[x].w;

    printf("%d\n",ans);
	
	return 0;
}

#include<bits/stdc++.h>
using namespace std;
const int N=1010;

struct Node{int fa,last,nxt,siz;double w,sw;}a[N];
priority_queue< pair<double ,int > >q;
bool vis[N];

int main()
{
    int n,rt;scanf("%d%d",&n,&rt);
    for(int i=1;i<=n;++i)
    {
        scanf("%lf",&a[i].w);
        a[i].last=i;
        a[i].sw=a[i].w;
        a[i].siz=1;
        if(i!=rt) q.push({a[i].w,i});
    }
    for(int i=1,x,y;i<n;++i) scanf("%d%d",&x,&y),a[y].fa=x;
    memset(vis,0,sizeof(vis));
    while(!q.empty())
    {
        int x=q.top().second;q.pop();
        if(vis[x]) continue;
        vis[x]=1;
        int tx=a[x].fa;while(vis[tx] && tx!=rt) tx=a[tx].fa;

        a[a[tx].last].nxt=x;
        a[tx].last=a[x].last;

        a[tx].siz+=a[x].siz;
        a[tx].sw+=a[x].sw;

        if(tx!=rt) q.push({ a[tx].sw/a[tx].siz , tx });
    }

    int ans=0;for(int i=1,x=rt;i<=n;++i,x=a[x].nxt) ans+=i*a[x].w;

    printf("%d\n",ans);
	
	return 0;
}