#include <iostream>
#define NMAX 16005
#include <fstream>
#include <vector>
#include <cstdlib>
#include <deque>
using namespace std;

ifstream in("asmax.in");
ofstream out("asmax.out");

int n,l[NMAX],v[NMAX],viz[NMAX],x,y,Max,suma;
vector<int> a[NMAX];

void dfs(int nod)
{

    viz[nod] = 1;
    for(int i=0;i<a[nod].size();i++)
    {
        if(!viz[a[nod][i]])
        {
            dfs(a[nod][i]);
        }
    }
    suma = suma + v[nod];
    if(suma<0)
        suma = v[nod];
    if(Max<suma) Max = suma;
}

int main()
{
    in >> n;
    for(int i=1;i<=n;i++)
        in >> v[i];
    for(int i=1;i<n;i++)
    {
        in >> x >>y;
        a[x].push_back(y);
        a[y].push_back(x);
    }

    dfs(1);
    out << Max;
    return 0;
}