#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];
int scor[Nmax];

void calcScoruri(int node=1)
{
    visited[node]=1;
    vector<int> sums;
    for(auto nxtnode : muchii[node])
    {
        if(visited[nxtnode]==0)
        {
            calcScoruri(nxtnode);
            sums.push_back(scor[nxtnode]);
        }
    }
    if(sums.empty())
    {
        scor[node]=v[node];
        return;
    }

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

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

    int rez=v[node];
    if(rez<vmaxSingle+v[node])
        rez=vmaxSingle+v[node];
    if(rez<vmaxCompus+v[node])
        rez=vmaxCompus+v[node];
    scor[node]=rez;
    return;
}


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);
    }
    calcScoruri();
    int vmax=-INF;
    for(int i=1; i<=n; i++)
        vmax=max(vmax, scor[i]);
    fout<<vmax;
    return 0;
}