#include<bits/stdc++.h>
#define ll long long
using namespace std;
ll n,s,s1,s2,ans;
struct in
{
    ll so[1005],m,l;
}p[1005],x;
struct cmp
{
    bool operator ()(in a,in b)
    {
        return a.m<b.m;
    }
};
priority_queue<in,vector<in>,cmp> q;
inline ll read()
{
	ll x=0;
	char a;
	a=getchar();
	while(a<'0'||a>'9') a=getchar();
	while(a>='0'&&a<='9') 
	{
		x=(x<<3)+(x<<1)+(a^48);
		a=getchar();
	}
	return x;
} 
ll write(ll x)
{
	if(x/10) write(x/10);
	putchar(x-x/10*10+48);
}
void in()
{
	n=read();
	s=read();
	for(ll i=1;i<=n;i++)
	{
		p[i].m=read();
	}
	for(ll i=1;i<n;i++)
	{
		s1=read();
		s2=read();
		p[s1].so[p[s1].l++]=s2;
	}
	q.push(p[s]);
}
ll deal(ll t)
{ 
	x=q.top();
	ans+=x.m*t;
	q.pop();
	for(int i=0;i<x.l;i++)
	{
		q.push(p[x.so[i]]);
	}
	if(q.empty()) return ans;
	deal(++t);
}
int main()
{
	freopen("colortree.in","r",stdin);	
	freopen("colortree.out","w",stdout);
	in();
	write(deal(1));
	return 0;
}