#include <bits/stdc++.h>
using namespace std;
const int OO = 1e9;
const double EPS = 1e-9;
template <class T>
void _db(const char* dbStr, T e) {
  cout << dbStr << " = " << e << endl;
}
template <class T, class... L>
void _db(const char* dbStr, T e, L... r) {
  while (*dbStr != ',') cout << *dbStr++;
  cout << " = " << e << ',';
  _db(dbStr + 1, r...);
}
template <class S, class T>
ostream& operator<<(ostream& o, const map<S, T>& v) {
  o << "[";
  int i = 0;
  for (const pair<S, T>& pr : v)
    o << (!i++ ? "" : ", ") << "{" << pr.first << " : " << pr.second << "}";
  return o << "]";
}
template <template <class, class...> class S, class T, class... L>
ostream& operator<<(ostream& o, const S<T, L...>& v) {
  o << "[";
  int i = 0;
  for (const auto& e : v) o << (!i++ ? "" : ", ") << e;
  return o << "]";
}
template <class S, class T>
ostream& operator<<(ostream& o, const pair<S, T>& pr) {
  return o << "(" << pr.first << ", " << pr.second << ")";
}
ostream& operator<<(ostream& o, const string& s) {
  for (const char& c : s) o << c;
  return o;
}
template <class T>
using V = vector<T>;
template <class T>
using VV = V<V<T>>;
template <class T>
using VVV = VV<V<T>>;
using ll = long long;
using pii = pair<int, int>;
using vi = V<int>;
using vii = V<pii>;
using vvi = VV<int>;
using mii = map<int, int>;
using umii = unordered_map<int, int>;
using si = set<int>;
using usi = unordered_set<int>;
int n;
vi c;
vvi adj;
pii dfs(int u, int par) {
  int mxH[] = {0, 0, 0}, diam = 0;
  for (auto& v : adj[u])
    if (v != par) {
      pii pr = dfs(v, u);
      diam = max(diam, pr.first);
      mxH[0] = pr.second + (c[u] != c[v]);
      sort(mxH, mxH + 3);
    }
  diam = max(diam, mxH[1] + mxH[2]);
  return make_pair(diam, mxH[2]);
}
int main() {
  ios::sync_with_stdio(false);
  cout.precision(10);
  cin.tie(0);
  cin >> n;
  c.assign(n + 1, 0);
  adj.assign(n + 1, vi());
  for (int i = 1; i <= n; ++i) {
    cin >> c[i];
  }
  for (int i = 1; i <= n - 1; ++i) {
    int u, v;
    cin >> u >> v;
    adj[u].push_back(v);
    adj[v].push_back(u);
  }
  cout << (dfs(1, -1).first + 1) / 2 << '\n';
  return 0;
}
