#include <bits/stdc++.h>

using namespace std;

typedef long long ll;

template <typename T>
struct small_tree {
    int n;
    vector<T> t;
    void init(int _n) {
        n = _n + 5;
        t.assign(2 * n + 10, 0);
    }
    void update(int pos, T val) {
        for (t[pos += n] = val; pos > 1; pos >>= 1) {
            t[pos >> 1] = max(t[pos], t[pos ^ 1]);
        }
    }
    T get(int l, int r) {
        T res = 0;
        for (l += n, r += n; l <= r; l >>= 1, r >>= 1) {
            if (l & 1) res = max(res, t[l++]);
            if (!(r & 1)) res = max(res, t[r--]);
        }
        return res;
    }
};

vector<pair<int, int>> merge(const vector<pair<int, int>>& a, const vector<pair<int, int>>& b) {
    int n = a.size(), m = b.size();
    int i = 0, j = 0;
    vector<pair<int, int>> res;
    while (i < n && j < m) {
        if (a[i].first < b[j].first) {
            res.push_back(a[i++]);
        } else {
            res.push_back(b[j++]);
        }
    }
    while (i < n) {
        res.push_back(a[i++]);
    }
    while (j < m) {
        res.push_back(b[j++]);
    }
    return res;
}

template <typename T>
struct Node {
    small_tree<T> tree;
    int tl, tr;
    vector<pair<int, int>> all;
    vector<int> pos;
    Node(int x = 0, int y = 0) {
        tl = x;
        tr = x;
        all = {{y, x}};
        pos = {0};
        tree.init(1);
    }
    friend Node operator+(const Node& a, const Node& b) {
        Node res;
        res.tl = a.tl;
        res.tr = b.tr;
        res.all = merge(a.all, b.all);
        res.pos.resize(res.all.size());
        for (int i = 0; i < res.all.size(); i++) {
            res.pos[res.all[i].second - res.tl] = i;
        }
        res.tree.init(res.tr - res.tl + 1);
        return res;
    }
    void update(int x, T val) {
        assert(tl <= x && x <= tr);
        tree.update(pos[x - tl], val);
    }
    T get(int l, int r) {
        int L = lower_bound(all.begin(), all.end(), make_pair(l, 0)) - all.begin();
        int R = lower_bound(all.begin(), all.end(), make_pair(r + 1, 0)) - all.begin() - 1;
        L = max(0, L);
        R = min(R, tr - tl);
        if (L <= R) {
            return tree.get(L, R);
        } else {
            return 0;
        }
    }
};

template <typename T>
struct big_tree {
    static const int N = 2e5 + 10;
    int y_init[N];
    T t[4 * N];
    void build(int v = 1, int tl = 1, int tr = N - 1) {
        if (tl == tr) {
            t[v] = T(tl, y_init[tl]);
            return;
        }
        int tm = (tl + tr) / 2;
        build(v + v, tl, tm);
        build(v + v + 1, tm + 1, tr);
        t[v] = t[v + v] + t[v + v + 1];
    }
    void update(int x, int val, int v = 1, int tl = 1, int tr = N - 1) {
        if (x < tl || tr < x) return;
        t[v].update(x, val);
        if (tl == tr) {
            return;
        }
        int tm = (tl + tr) / 2;
        update(x, val, v + v, tl, tm);
        update(x, val, v + v + 1, tm + 1, tr);
    }
    int get(int lx, int rx, int ly, int ry, int v = 1, int tl = 1, int tr = N - 1) {
        if (tr < lx || rx < tl) return 0;
        if (lx <= tl && tr <= rx) {
            return t[v].get(ly, ry);
        }
        int tm = (tl + tr) / 2;
        return max(get(lx, rx, ly, ry, v + v, tl, tm), get(lx, rx, ly, ry, v + v + 1, tm + 1, tr));
    }
};

big_tree<Node<int>> tree;

const int N = 2e5 + 10;
const int L = 20;
int c[N];
vector<int> g[N];
vector<int> pos[N];

int in[N], out[N];
int up[N][L];
int timer;
int depth[N];

void dfs_lca(int v = 1, int p = 1) {
    in[v] = ++timer;
    up[v][0] = p;
    for (int i = 1; i < L; i++) {
        up[v][i] = up[up[v][i - 1]][i - 1];
    }
    for (int to : g[v]) {
        if (to != p) {
            depth[to] = depth[v] + 1;
            dfs_lca(to, v);
        }
    }
    out[v] = timer;
}

bool is_anc(int u, int v) {
    return in[u] <= in[v] && in[v] <= out[u];
}

int lca(int u, int v) {
    if (is_anc(u, v)) return u;
    else if (is_anc(v, u)) return v;
    for (int i = L - 1; i >= 0; i--) {
        if (!is_anc(up[u][i], v)) u = up[u][i];
    }
    return up[u][0];
}

int dist(int u, int v) {
    return depth[u] + depth[v] - 2 * depth[lca(u, v)];
}

int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);
#ifdef LOCAL
    freopen("input.txt", "r", stdin);
#endif

    int n;
    cin >> n;
    for (int i = 1; i <= n; i++) {
        cin >> c[i];
    }
    for (int i = 1; i <= n - 1; i++) {
        int u, v;
        cin >> u >> v;
        g[u].push_back(v);
        g[v].push_back(u);
    }
    dfs_lca(1, 1);
    vector<tuple<int, int, int>> vec;
    for (int i = 1; i <= n; i++) {
        pos[c[i]].push_back(i);
    }
    for (int i = 1; i <= n; i++) {
        if (pos[i].size() == 2) {
            int u = pos[i][0], v = pos[i][1];
            if (in[u] > in[v]) {
                swap(u, v);
            }
            vec.emplace_back(dist(u, v), u, v);
        }
    }
    sort(vec.rbegin(), vec.rend());

    for (auto [d, u, v] : vec) {
        tree.y_init[in[u]] = in[v];
        tree.y_init[in[v]] = in[u];
    }
    tree.build();

    int ans = 0;
    for (auto [d, u, v] : vec) {
        int cur = 0;

        if (is_anc(u, v)) {
            int w = 0;
            for (int to : g[u]) {
                if (is_anc(u, to) && is_anc(to, v)) {
                    w = to;
                }
            }
            cur = max({cur, tree.get(1, in[w] - 1, in[v], out[v]), tree.get(out[w] + 1, n, in[v], out[v])});
        } else {
            cur = max(cur, tree.get(in[u], out[u], in[v], out[v]));
        }
        cur += 2;
        tree.update(in[u], cur);
        tree.update(in[v], cur);
        ans = max(ans, d >= 2 ? cur + 1 : cur);
    }
    cout << ans << "\n";

#ifdef LOCAL
    cout << "\nTime elapsed: " << double(clock()) / CLOCKS_PER_SEC << " s.\n";
#endif
}