#include <cstdio>
#include <cmath>
#include <cstdlib>
#include <cassert>
#include <ctime>
#include <cstring>
#include <string>
#include <set>
#include <map>
#include <vector>
#include <list>
#include <deque>
#include <queue>
#include <sstream>
#include <iostream>
#include <algorithm>

using namespace std;

#define pb push_back
#define mp make_pair
#define fs first
#define sc second

const double pi = acos(-1.0);
const int size = 1000 * 1000 + 100;

int n;
long long a[size];
long long insubtree[size];
long long longest[size];
long long ans = 0;

vector <int> vertex[size];

void dfs1(int v, int f) {
    vector <long long> mxs;
    longest[v] = a[v];
    insubtree[v] = a[v];
    for (int i = 0; i < (int) vertex[v].size(); i++) {
        if (vertex[v][i] != f) {
            dfs1(vertex[v][i], v);
            longest[v] = max(longest[v], longest[vertex[v][i]] + a[v]);
            insubtree[v] = max(insubtree[v], insubtree[vertex[v][i]]);
            mxs.pb(longest[vertex[v][i]]);
        }
    }

    sort(mxs.rbegin(), mxs.rend());

    if ((int) mxs.size() > 0) {
        insubtree[v] = max(insubtree[v], mxs[0] + a[v]);
    }
    if ((int) mxs.size() > 1) {
        insubtree[v] = max(insubtree[v], mxs[0] + mxs[1] + a[v]);
    }
}

void dfs2(int v, int f, long long best, long long lgt) {
    ans = max(ans, insubtree[v] + best);

    set <pair <long long, int> > bestset;
    set <pair <long long, int> > lgtset;
    bestset.insert(mp(best, -1));
    lgtset.insert(mp(lgt, -1));

    for (int i = 0; i < (int) vertex[v].size(); i++) {
        if (vertex[v][i] != f) {
            bestset.insert(mp(insubtree[vertex[v][i]], i));
            lgtset.insert(mp(longest[vertex[v][i]], i));
        }
    }

    for (int i = 0; i < (int) vertex[v].size(); i++) {
        if (vertex[v][i] != f) {
            bestset.erase(mp(insubtree[vertex[v][i]], i));
            lgtset.erase(mp(longest[vertex[v][i]], i));

            long long nb = bestset.rbegin()->fs;
            long long curb = a[v];
            set <pair <long long, int> >::iterator it = lgtset.end();
            if (lgtset.size() > 0) {
                --it;
                curb += it->fs;
            }
            if (lgtset.size() > 1) {
                --it;
                curb += it->fs;
            }

            dfs2(vertex[v][i], v, max(nb, curb), lgtset.rbegin()->fs + a[v]);

            bestset.insert(mp(insubtree[vertex[v][i]], i));
            lgtset.insert(mp(longest[vertex[v][i]], i));
        }
    }
}

int main() {
    scanf("%d", &n);
    for (int i = 0; i < n; i++)
        scanf("%lld", &a[i]);

    for (int i = 0; i < n - 1; i++) {
        int v, u;

        scanf("%d%d", &u, &v);
        u--, v--;

        vertex[v].pb(u);
        vertex[u].pb(v);
    }

    dfs1(0, -1);
    ans = 0ll;

    dfs2(0, -1, 0ll, 0ll);

    printf("%lld\n", ans);

    return 0;
}