#include <iostream>
#include <vector>
#include <algorithm>
#include <queue>
#include <set>
#include <map>
#define INF 1e9
using namespace std;
typedef long long ll;
int n = 0, k = 0;
int c[200005], dp[200005], root[200005], p[200005];
bool visited[200005], processed[200005];
vector<int>adj[200005], v[200005];
queue<int>q;
int get_size(int s, int e) {
dp[s] = 1;
for (auto u : adj[s]) {
if (u == e || visited[u])continue;
get_size(u, s);
dp[s] += dp[u];
}
return dp[s];
}
int get_centroid(int s, int e, int n) {
for (auto u : adj[s]) {
if (u == e || visited[u])continue;
if (dp[u] * 2 > n) return get_centroid(u, s, n);
}
return s;
}
void dfs(int s, int e = 0) {
p[s] = e;
processed[c[s]] = 0;
root[s] = (e == 0 ? s : root[e]);
for (int u : adj[s]) {
if (u != e && !visited[u]) {
dfs(u, s);
}
}
}
int centroid_decomp(int node) {
int centroid = get_centroid(node, 0, get_size(node, 0));
visited[centroid] = true;
dfs(centroid);
q.push(c[centroid]);
int ans = 0;
while (q.size()) {
int col = q.front();q.pop();
if (processed[col]) continue;
processed[col] = true;
for (int u : v[col]) {
if (root[u] != centroid) {
ans = k;
break;
}
if (p[u] != 0) q.push(c[p[u]]);
}
ans++;
}
//cout << centroid << " " << ans << "\n";
for (int u : adj[centroid]) {
if (!visited[u]) ans = min(ans, centroid_decomp(u));
}
return ans;
}
void solve()
{
cin >> n >> k;
for (int i = 1; i <= n - 1; i++) {
int u, v; cin >> u >> v;
adj[u].push_back(v);
adj[v].push_back(u);
}
for (int i = 1; i <= n; i++) { cin >> c[i]; v[c[i]].push_back(i); }
cout << centroid_decomp(1) - 1 << "\n";
}
int main()
{
ios_base::sync_with_stdio(0);
cin.tie(0);
int t = 1;// cin>>t;
while (t--) solve();
return 0;
}
