#include <bits/stdc++.h>
inline int two(int n) { return 1 << n; }
inline int test(int n, int b) { return (n >> b) & 1; }
inline void set_bit(int& n, int b) { n |= two(b); }
inline void unset_bit(int& n, int b) { n &= ~two(b); }
inline int last_bit(int n) { return n & (-n); }
inline int ones(int n) {
  int res = 0;
  while (n && ++res) n -= n & (-n);
  return res;
}
long long int gcd(long long int a, long long int b) {
  return (a ? gcd(b % a, a) : b);
}
long long int modPow(long long int a, long long int b, long long int MOD) {
  long long int x = 1, y = a;
  while (b > 0) {
    if (b % 2 == 1) {
      x = (x * y) % MOD;
    }
    b /= 2;
    y = (y * y) % MOD;
  }
  return x;
}
long long int modInverse(long long int a, long long int p) {
  return modPow(a, p - 2, p);
}
using namespace std;
const int N = 2e5 + 5;
vector<int> adj[N];
int dist[N], marked[N], col[N];
void BFS(int src, int n) {
  memset(marked, 0, sizeof(marked));
  for (auto i = (1); i <= (n); i++) dist[i] = INT_MAX;
  dist[src] = 0;
  queue<int> Q;
  Q.push(src);
  marked[src] = 1;
  while (!Q.empty()) {
    int top = Q.front();
    Q.pop();
    for (auto child : adj[top]) {
      if (!marked[child]) {
        marked[child] = 1;
        dist[child] = dist[top] + (col[top] ^ col[child]);
        Q.push(child);
      }
    }
  }
}
int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  int n, u, v;
  cin >> n;
  for (auto i = (1); i <= (n); i++) cin >> col[i];
  for (auto i = (1); i <= (n - 1); i++) {
    cin >> u >> v;
    adj[u].push_back(v);
    adj[v].push_back(u);
  }
  BFS(1, n);
  int vv = 1;
  for (auto i = (1); i <= (n); i++) {
    if (dist[i] > dist[vv]) vv = i;
  }
  BFS(vv, n);
  vv = 1;
  for (auto i = (1); i <= (n); i++) {
    if (dist[i] > dist[vv]) vv = i;
  }
  cout << (dist[vv] + 1) / 2;
  return 0;
}
