from collections import defaultdict
from functools import cache
import sys
sys.setrecursionlimit(10**6)

N = int(input())
S = list(map(int, input().split()))

adj = defaultdict(list)
for _ in range(N-1):
    a, b = map(lambda x: int(x)-1, input().split())
    adj[a].append(b)
    adj[b].append(a)


@cache
def dfs(v):
    s = S[v]
    res = s
    for to in adj[v]:
        if s <= S[to]: continue
        res = max(res, s + dfs(to))

    return res


ans = 0
for i in range(N):
    ans = max(ans, dfs(i))

print(ans)