#include <iostream>

#include <cstdio>

#include <algorithm>

#include <cstring>

#include <cmath>

#include <set>

#define LL long long

using namespace std;

const int MAXN = 100050;

const int MOD = 1e9 + 7;

LL ans;

LL ma[MAXN], t[MAXN], sum[MAXN];

LL l[MAXN], ml[MAXN], r[MAXN], mr[MAXN];

bool leaf[MAXN];

LL mm[10];

bool vis[MAXN];

int head[MAXN];

struct Edge{

	int u, v;

	int next;

}edge[MAXN * 2];

int weight[MAXN], par[MAXN];

int n, tot;

void addedge(int u, int v){

	edge[tot].u = u;

	edge[tot].v = v;

	edge[tot].next = head[u];

	head[u] = tot++;

}

void dfs(int u){

	vis[u] = true;

	leaf[u] = true;

	for(int e = head[u]; e != -1; e = edge[e].next){

		int v = edge[e].v;

		if(vis[v]) continue;

		par[v] = u;

		dfs(v);

		leaf[u] = false;

	}

}

void slove(int u){

	if(leaf[u]){

		ma[u] = t[u] = sum[u] = weight[u];

		return ;

	}

	LL m1, m2, M1, M2;

	m1 = m2 = M1 = M2 = 0;

	for(int e = head[u]; e != -1; e = edge[e].next){

		int v = edge[e].v;

		if(v != par[u]){

			slove(v);

			if(ma[v] >= M1){

				M2 = M1, M1 = ma[v];

			}

			else if(ma[v] > M2){

				M2 = ma[v];

			}

			if(sum[v] >= m1){

				m2 = m1, m1 = sum[v];

			}

			else if(sum[v] > m2){

				m2 = sum[v];

			}

			t[u] = max(t[u], t[v] + weight[u]);

		}

	}

	ma[u] = max(M1, m1 + m2 + weight[u]);

	sum[u] = m1 + weight[u];

	ans = max(ans, M1 + M2);

	int counts = 0;

	for(int e = head[u]; e != -1; e = edge[e].next){

		int v = edge[e].v;

		if(v != par[u]){

			l[++counts] = sum[v];

			r[counts] = sum[v];

		}

	}

	l[0] = ml[0] = r[counts + 1] = mr[counts + 1] = 0;

	//从左往右寻找最大的两个sum

	for(int i = 1; i <= counts ; i++){

		if(l[i] > l[i - 1]) ml[i] = l[i - 1];

		else if(l[i] > ml[i - 1]){

			ml[i] = l[i];

			l[i] = l[i - 1];

		}

		else{

			l[i] = l[i - 1], ml[i] = ml[i - 1];

		}

	}

	//从右往左。。。。

	for(int i = counts; i >= 1; i--){

		if(r[i] > r[i + 1]) mr[i] = r[i + 1];

		else if(r[i] > mr[i + 1]){

			mr[i] = r[i];

			r[i] = r[i + 1];

		}

		else{

			r[i] = r[i + 1], mr[i] = mr[i + 1];

		}

	}

	counts = 0;

	for(int e = head[u]; e != -1; e = edge[e].next){

		int v = edge[e].v;

		if(v == par[u]) continue;

		counts ++;

		mm[0] = l[counts - 1], mm[1] = ml[counts - 1];

		mm[2] = r[counts + 1], mm[3] = mr[counts + 1];

		sort(mm, mm + 4);

		ans = max(ans, weight[u] + ma[v] + mm[3] + mm[2]);

		ans = max(ans, weight[u] + mm[3] + t[v]);

		t[u] = max(t[u], ma[v] + weight[u] + mm[3]);

	}

}

int main(){

	scanf("%d", &n);

	memset(head, -1, sizeof(head));

//	memset(vis, false, sizeof(vis));

//	memset(leaf, false, sizeof(leaf));

	tot = 0;

	memset(t, 0, sizeof(t));

	for(int i = 1; i <= n; i++){

		scanf("%d", &weight[i]);

	}

	int u, v;

	memset(par, -1, sizeof(par));

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

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

		addedge(u, v);

		addedge(v, u);

	}

	dfs(1);

	ans = 0;

	slove(1);

	cout << ans << endl;

}