#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define F first
#define S second
#define pb push_back
#define pii pair<int, int>
const int N = 2e5 + 5;
int n, k;
vector<int> g[N];
int del[N];
int sz[N];
int par[N];
int c[N];
int vis[N];
int cnt_col[N];
vector<int> col[N];
vector<int> cand;
vector<int> vec;
int res = 1e9;
void pre_dfs(int u, int p) {
sz[u] = 1;
for (int v : g[u]) {
if (v == p || del[v]) continue;
pre_dfs(v, u);
sz[u] += sz[v];
}
}
int find_centroid(int u, int p, int n) {
for (int v : g[u]) {
if (v == p || del[v]) continue;
if (sz[v] > n / 2) return find_centroid(v, u, n);
}
return u;
}
void dfs(int u, int p, int root) {
par[u] = p;
if (c[u] == c[root]) cand.pb(u);
vec.pb(u);
cnt_col[c[u]]++;
for (int v : g[u]) {
if (v == p || del[v]) continue;
dfs(v, u, root);
}
}
void solve(int u) {
pre_dfs(u, 0);
int n = sz[u];
int root = find_centroid(u, 0, n);
dfs(root, 0, root);
del[root] = 1;
for (int v : cand) {
vis[v] = 1;
}
if (cnt_col[c[root]] == col[c[root]].size()) {
int ans = 0;
while(!cand.empty()) {
int cur = cand.back();
cand.pop_back();
int v = par[cur];
while(!vis[v] && v != 0) {
if (cnt_col[c[v]] != col[c[v]].size()) {
ans = 1e9;
break;
}
for (int x : col[c[v]]) {
cand.pb(x);
vis[x] = 1;
}
ans++;
v = par[v];
}
if (ans == 1e9) break;
}
// cout << root << ' ' << ans << ":\n";
// for (int x : vec) {
// cout << x << ' ';
// } cout << '\n';
res = min(res, ans);
}
// cout << root << ":\n";
for (int v : vec) {
// cout << v << ' ';
vis[v] = 0;
cnt_col[c[v]] = 0;
}
// cout << '\n';
cand.clear();
vec.clear();
for (int v : g[root]) {
if (del[v]) continue;
solve(v);
}
}
signed main() {
ios_base::sync_with_stdio(0);
cin.tie(0);
cin >> n >> k;
for (int i = 1; i < n; i++) {
int u, v;
cin >> u >> v;
g[u].pb(v);
g[v].pb(u);
}
for (int i = 1; i <= n; i++) {
cin >> c[i];
col[c[i]].pb(i);
}
solve(1);
cout << res;
}
