from collections import deque

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

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

ret = [0] * N
que = deque([])
for i in range(N):
    if indeg[i] == 0:
        que.append(i)
        ret[i] = S[i]

while que:
    x = que.popleft()
    for nx in G[x]:
        ret[nx] = max(ret[nx], ret[x] + S[nx])
        indeg[nx] -= 1
        if indeg[nx] == 0:
            que.append(nx)

print(max(ret))