#include <bits/stdc++.h>
#define gcd         __gcd
#define bitcount    __builtin_popcountll
#define rep(i,j,n)  for(i=j;i<n;i++)
#define tr(it,c)    for(auto it=(c).begin();it!=(c).end();it++)
#define pb          push_back
#define mp          make_pair
#define hell        1000000007
#define uset        unordered_set
#define umap        unordered_map
#define ft          first
#define sc          second
using namespace std;
typedef long long ll;
typedef pair<ll,ll> pl;

template <class T> T& get(T &n) {
    cin>>n;
    return n;
}

struct edge{
    int n[2];
    inline int& operator[](int i){
        assert(i==0 || i==1);
        return n[i];
    }
};

struct Tree{
    int N;
    vector<ll> a;
    vector<edge> e;
    vector<vector<int>> adj;
    vector<vector<pl>> dp;
    vector<vector<ll>> dp2;
    Tree(int N):N(N),a(N),e(N-1),adj(N),dp(N-1,vector<pl>(2,mp(-1LL,-1LL))),dp2(N-1,vector<ll>(2,-1LL)){
    }
    ll solve(int i,int idx){ // returns best but computes both best and second best
        int u=e[i][idx];
        auto ref=&dp[i][idx];
        if(*ref==mp(-1LL,-1LL)){
            priority_queue<ll,vector<ll>,greater<ll>> q;
            for(auto j:adj[u]){
                if(i==j) continue;
                int v=e[j][0]^e[j][1]^u;
                ll p=solve(j,(e[j][0]==v?0:1));
                q.push(p);
                if(q.size()>2) q.pop();
            }
            q.push(0);q.push(0);
            while(q.size()>2) q.pop();
            ref->sc=q.top()+a[u];q.pop();
            ref->ft=q.top()+a[u];q.pop();
        }
        return ref->ft;
    }
    ll solve2(int i,int idx){
        int u=e[i][idx];
        auto ref=&dp2[i][idx];
        if(*ref==-1LL){
            ll ans=dp[i][idx].ft+dp[i][idx].sc-a[u];
            for(auto j:adj[u]){
                if(i==j) continue;
                int v=e[j][0]^e[j][1]^u;
                ll p=solve2(j,(e[j][0]==v?0:1));
                ans=max(p,ans);
            }
            *ref=ans;
        }
        return *ref;
    }
    ll solve3(){
        ll ans=0;
        for(int i=0;i<N-1;i++){
            ans=max(ans,dp2[i][0]+dp2[i][1]);
        }
        return ans;
    }
};

int main() {
    int N,i;
    ios::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);
    cin>>N;
    Tree t(N);
    rep(i,0,N){
        get(t.a[i]);
    }
    rep(i,0,N-1){
        int u=--get(t.e[i][0]);
        int v=--get(t.e[i][1]);
        t.adj[u].push_back(i);
        t.adj[v].push_back(i);
    }
    rep(i,0,N-1){
        t.solve(i,0);
        t.solve(i,1);
    }
    rep(i,0,N-1){
        t.solve2(i,0);
        t.solve2(i,1);
    }
    cout<<t.solve3()<<endl;
    return 0;
}