import sys
input = sys.stdin.readline
N = int(input())
S = list(map(int,input().split()))
AB = [tuple(map(int,input().split())) for _ in range(N-1)]

G = [[] for _ in range(N)]
indeg = [0]*N
for a,b in AB:
    a,b = a-1,b-1
    if S[a] > S[b]:
        G[a].append(b)
        indeg[b] += 1
    elif S[a] < S[b]:
        G[b].append(a)
        indeg[a] += 1

from collections import deque
q = deque()
score = S[:]
for i in range(N):
    if indeg[i]==0:
        q.append(i)
while q:
    v = q.popleft()
    for to in G[v]:
        indeg[to] -= 1
        score[to] = max(score[to], score[v] + S[to])
        if indeg[to] == 0:
            q.append(to)
print(max(score))