#include <bits/stdc++.h>
using namespace std;
struct Edge {
  int u, v;
} e[200050 << 1];
int fa[200050];
int n, color[200050], s, d;
int cnt[2], dis[200050];
bool vis[200050];
vector<int> G[200050];
int find(int x) {
  if (x == fa[x]) return x;
  return fa[x] = find(fa[x]);
}
void _union(int x, int y) {
  int f1 = find(x);
  int f2 = find(y);
  if (f1 == f2) return;
  if (f1 < f2)
    fa[f2] = f1;
  else
    fa[f1] = f2;
}
queue<int> q;
void bfs(int u) {
  memset(vis, false, sizeof(vis));
  memset(dis, 0, sizeof(dis));
  while (!q.empty()) q.pop();
  q.push(u);
  vis[u] = true;
  while (!q.empty()) {
    int now = q.front();
    q.pop();
    for (int i = 0; i < G[now].size(); i++) {
      int v = G[now][i];
      if (!vis[v]) {
        q.push(v);
        vis[v] = true;
        s = v;
        dis[v] = dis[now] + 1;
      }
    }
  }
}
int main() {
  scanf("%d", &n);
  for (int i = 1; i <= n; i++) {
    scanf("%d", &color[i]);
    fa[i] = i;
  }
  for (int i = 1; i < n; i++) {
    int u, v;
    scanf("%d%d", &u, &v);
    e[2 * i - 1].u = u;
    e[2 * i - 1].v = v;
    e[i * 2].u = v;
    e[i * 2].v = u;
    if (color[u] == color[v]) _union(u, v);
  }
  for (int i = 1; i <= n; i++) fa[i] = find(i);
  for (int i = 1; i < n; i++) {
    int u = e[i * 2 - 1].u, v = e[i * 2 - 1].v;
    if (fa[u] != fa[v]) {
      G[fa[u]].push_back(fa[v]);
      G[fa[v]].push_back(fa[u]);
    }
  }
  int i = 1;
  for (; G[i].size() == 0 && i <= n; i++)
    ;
  if (i > n) {
    printf("0\n");
    return 0;
  }
  bfs(i);
  bfs(s);
  printf("%d\n", (dis[s] + 1) / 2);
  return 0;
}
