#include <bits/stdc++.h>
using namespace std;
#ifdef ngu
#include "debug.h"
#else
#define debug(...) 42
#endif
const int N = (int) 2e5 + 5;
const int INF = (int) 1e6;
int n;
int p[N], h[N];
int tin[N], tout[N], pos[N];
vector<int> g[N];
namespace lca {
const int LOG = 19;
int tin[N], tout[N];
int lg[N << 1];
int spt[LOG][N << 1];
int order;
void dfs(int u, int p) {
spt[0][tin[u] = ++order] = u;
for (int v : g[u]) {
if (v != p) {
dfs(v, u);
spt[0][++order] = u;
}
}
tout[u] = order;
}
int min_by_time(int u, int v) {
return tin[u] < tin[v] ? u : v;
}
void build() {
dfs(1, 1);
for (int i = 2; i <= order; ++i) {
lg[i] = lg[i / 2] + 1;
}
for (int j = 1; j <= lg[order]; ++j) {
for (int i = 1; i + (1 << j) - 1 <= order; ++i) {
spt[j][i] = min_by_time(spt[j - 1][i], spt[j - 1][i + (1 << (j - 1))]);
}
}
}
int get(int u, int v) {
int l = min(tin[u], tin[v]);
int r = max(tout[u], tout[v]);
int k = lg[r - l + 1];
return min_by_time(spt[k][l], spt[k][r - (1 << k) + 1]);
}
}
int order;
void pre_dfs(int u) {
pos[tin[u] = ++order] = u;
for (int v : g[u]) {
if (!tin[v]) {
h[v] = h[u] + 1;
pre_dfs(v);
}
}
tout[u] = order;
}
int dis(int u, int v) {
return h[u] + h[v] - 2 * h[lca::get(u, v)];;
}
struct segment_tree {
int n;
vector<long long> s, lz;
vector<int> res;
segment_tree() {};
segment_tree(int n): n(n) {
s.resize(4 << __lg(n));
lz.resize(4 << __lg(n));
res.resize(4 << __lg(n));
}
void pull(int id) {
s[id] = max(s[id << 1], s[id << 1 | 1]);
res[id] = s[id << 1] > s[id << 1 | 1] ? res[id << 1] : res[id << 1 | 1];
}
void build(int id, int l, int r) {
if (l == r) {
res[id] = pos[l];
s[id] = p[pos[l]];
return;
}
int mid = l + r >> 1;
build(id << 1, l, mid);
build(id << 1 | 1, mid + 1, r);
pull(id);
}
void build() {
build(1, 1, n);
}
void modify(int id, int x) {
s[id] += x;
lz[id] += x;
}
void push(int id) {
if (lz[id]) {
modify(id << 1, lz[id]);
modify(id << 1 | 1, lz[id]);
lz[id] = 0;
}
}
void upd(int id, int l, int r, int u, int v, int x) {
if (u <= l && r <= v) {
modify(id, x);
return;
}
int mid = l + r >> 1;
push(id);
if (u <= mid) {
upd(id << 1, l, mid, u, v, x);
}
if (mid < v) {
upd(id << 1 | 1, mid + 1, r, u, v, x);
}
pull(id);
}
void upd(int u, int v, int x) {
upd(1, 1, n, u, v, x);
}
int get() {
return s[1] > 0 ? res[1] : -1;
}
} st;
long long solve(int u) {
long long res = 0;
st.upd(tin[u], tout[u], -INF);
int x = st.get();
if (x != -1) {
res = max(res, solve(x) + dis(u, x));
}
st.upd(tin[u], tout[u], INF);
for (int v : g[u]) {
if (tin[v] > tin[u]) {
if (1 <= tin[v] - 1) {
st.upd(1, tin[v] - 1, -INF);
}
if (tout[v] + 1 <= n) {
st.upd(tout[v] + 1, n, -INF);
}
int x = st.get();
if (x != -1) {
res = max(res, solve(x) + dis(u, x));
}
if (1 <= tin[v] - 1) {
st.upd(1, tin[v] - 1, INF);
}
if (tout[v] + 1 <= n) {
st.upd(tout[v] + 1, n, INF);
}
}
}
return res;
}
signed main() {
ios::sync_with_stdio(false);
cin.tie(0);
#ifdef ngu
freopen("test.inp", "r", stdin);
freopen("test.out", "w", stdout);
#endif
cin >> n;
st = segment_tree(n);
for (int i = 1; i <= n; ++i) {
cin >> p[i];
}
for (int i = 1; i < n; ++i) {
int u, v;
cin >> u >> v;
g[u].emplace_back(v);
g[v].emplace_back(u);
}
lca::build();
pre_dfs(1);
st.build();
cout << solve(st.get());
}
