#include <cstdio>
#include <iostream>
#include <algorithm>
#include <cstring>
#include <vector>
using namespace std;
#define N 100010
#define lson(x) x<<1
#define rson(x) x<<1|1
int n,root=1;
int val[N]={0};
int f[N]={0},wson[N]={0};
vector<int> E[N];

void dfs(int rt,int father)
{
    int i,SON;
    wson[rt]=0;
    f[rt]=val[rt];
    for(i=0;i<E[rt].size();i++)
    {
        SON=E[rt][i];
        if(SON==father) continue;
        dfs(SON,rt);
        f[rt]=max(f[rt],f[rt]+wson[SON]);
        wson[rt]=max(wson[rt],max(wson[rt]+f[SON],wson[rt]+wson[SON]));
    }
    return ;
}

int main()
{
    freopen("profitz.in","r",stdin);
    freopen("profitz.out","w",stdout);
    scanf("%d",&n);
    int i,u,v;
    for(i=1;i<=n;i++)
        scanf("%d",&val[i]);
    for(i=1;i<n;i++)
    {
        scanf("%d%d",&v,&u);
        E[v].push_back(u);
        E[u].push_back(v);
    }
    dfs(root,0);
    int maxx=max(f[root],wson[root]);
    printf("%d\n",maxx);
    return 0;
}