package main

import (
	"bufio"
	"fmt"
	"os"
)

var (
	scanner = bufio.NewScanner(os.Stdin)
)

func init() {
	scanner.Split(bufio.ScanWords)
	scanner.Buffer(make([]byte, 1024*1024), 1024*1024*10)
}

func nextInt() int {
	scanner.Scan()
	res := 0
	for _, b := range scanner.Bytes() {
		res = res*10 + int(b-'0')
	}
	return res
}

func nextInt64() int64 {
	scanner.Scan()
	var res int64
	for _, b := range scanner.Bytes() {
		res = res*10 + int64(b-'0')
	}
	return res
}

func max(a, b int64) int64 {
	if a > b {
		return a
	}
	return b
}

type Top3 struct {
	v  [3]int64
	id [3]int
}

func (t *Top3) add(val int64, id int) {
	if val > t.v[0] {
		t.v[2], t.id[2] = t.v[1], t.id[1]
		t.v[1], t.id[1] = t.v[0], t.id[0]
		t.v[0], t.id[0] = val, id
	} else if val > t.v[1] {
		t.v[2], t.id[2] = t.v[1], t.id[1]
		t.v[1], t.id[1] = val, id
	} else if val > t.v[2] {
		t.v[2], t.id[2] = val, id
	}
}

func main() {
	if !scanner.Scan() {
		return
	}
	n := 0
	for _, b := range scanner.Bytes() {
		n = n*10 + int(b-'0')
	}

	a := make([]int64, n+1)
	for i := 1; i <= n; i++ {
		a[i] = nextInt64()
	}

	adj := make([][]int, n+1)
	for i := 0; i < n-1; i++ {
		u := nextInt()
		v := nextInt()
		adj[u] = append(adj[u], v)
		adj[v] = append(adj[v], u)
	}

	m1 := make([]int64, n+1)
	m2 := make([]int64, n+1)
	m3 := make([]int64, n+1)

	var dfs1 func(u, p int)
	dfs1 = func(u, p int) {
		var max_m2, second_max_m2 int64
		for _, v := range adj[u] {
			if v == p {
				continue
			}
			dfs1(v, u)
			m1[u] = max(m1[u], m1[v])

			val := max(0, m2[v])
			if val > max_m2 {
				second_max_m2 = max_m2
				max_m2 = val
			} else if val > second_max_m2 {
				second_max_m2 = val
			}
		}

		m2[u] = a[u] + max_m2
		m3[u] = a[u] + max_m2 + second_max_m2
		m1[u] = max(m1[u], m3[u])
	}

	dfs1(1, 0)

	var ans int64
	var dfs2 func(u, p int, out1, out2 int64)
	dfs2 = func(u, p int, out1, out2 int64) {
		top2_val1 := Top3{v: [3]int64{0, 0, 0}, id: [3]int{-1, -1, -1}}
		top3_val2 := Top3{v: [3]int64{0, 0, 0}, id: [3]int{-1, -1, -1}}

		if p != 0 {
			top2_val1.add(out1, p)
			top3_val2.add(max(0, out2), p)
		}
		for _, v := range adj[u] {
			if v != p {
				top2_val1.add(m1[v], v)
				top3_val2.add(max(0, m2[v]), v)
			}
		}

		for _, v := range adj[u] {
			if v == p {
				continue
			}

			max_val1_ex := top2_val1.v[0]
			if top2_val1.id[0] == v {
				max_val1_ex = top2_val1.v[1]
			}

			var m2_ex_1, m2_ex_2 int64
			if top3_val2.id[0] == v {
				m2_ex_1 = top3_val2.v[1]
				m2_ex_2 = top3_val2.v[2]
			} else if top3_val2.id[1] == v {
				m2_ex_1 = top3_val2.v[0]
				m2_ex_2 = top3_val2.v[2]
			} else {
				m2_ex_1 = top3_val2.v[0]
				m2_ex_2 = top3_val2.v[1]
			}

			new_out2 := a[u] + m2_ex_1
			new_out3 := a[u] + m2_ex_1 + m2_ex_2
			new_out1 := max(max_val1_ex, new_out3)

			ans = max(ans, m1[v]+new_out1)
			dfs2(v, u, new_out1, new_out2)
		}
	}

	dfs2(1, 0, 0, 0)
	fmt.Println(ans)
}