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

try:
    import pypyjit
    pypyjit.set_param('max_unroll_recursion=-1')
except ModuleNotFoundError:
    pass

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

adj = defaultdict(list)
adj2 = 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)

    if S[a] > S[b]:
        adj2[a].append(b)
    if S[a] < S[b]:
        adj2[b].append(a)


def dfs(v):
    s = S[v]
    res = s
    for to in adj2[v]:
        res = max(res, s + dfs(to))

    return res


ans = 0
for i in range(N):
    b = True
    small = False
    for to in adj[i]:
        if S[to] > S[i]:
            b = False
            break

        if S[to] < S[i]:
            small = True

    if b and small:
        ans = max(ans, dfs(i))

print(ans)