#include <bits/stdc++.h>

using namespace std;

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

const int Nmax=16001;
const int INF=20000000;

bitset<Nmax> visited;
forward_list<int> muchii[Nmax];
short int v[Nmax];

pair<int, bool> getSumMax(int node)
{
    visited[node]=1;
    vector<pair<int, bool>> sums;
    for(auto nxtnode : muchii[node])
    {
        if(visited[nxtnode]==0)
        {
            sums.push_back(getSumMax(nxtnode));
        }
    }
    if(sums.empty())
    {
        return make_pair(v[node], 1);
    }

    int vmaxSingle=-INF;
    for(unsigned int i=0; i<sums.size(); i++)
    {
        if(sums[i].first>vmaxSingle)
            vmaxSingle=sums[i].first;
    }

    int vmaxCompus=-INF;
    for(unsigned int i=0; i<sums.size(); i++)
    {
        if(sums[i].second==0)
            continue;
        if(vmaxCompus==-INF)
        {
            vmaxCompus=sums[i].first;
            continue;
        }
        if(sums[i].first>=0)
        {
            vmaxCompus+=sums[i].first;
        }
    }

    int rez=v[node]; bool canConc=1;
    if(rez<vmaxSingle)
    {
        rez=vmaxSingle;
        canConc=0;
    }
    if(rez<vmaxSingle+v[node])
    {
        rez=vmaxSingle+v[node];
        canConc=1;
    }
    if(rez<vmaxCompus+v[node])
    {
        rez=vmaxCompus+v[node];
        canConc=1;
    }
    return make_pair(rez, canConc);

}


int main()
{
    int n;
    fin>>n;
    for(int i=1; i<=n; i++)
        fin>>v[i];
    int x,y;
    for(int i=1; i<n; i++)
    {
        fin>>x>>y;
        muchii[x].push_front(y);
        muchii[y].push_front(x);
    }
    fout<<getSumMax(1).first;
    return 0;
}