#include <bits/stdc++.h>
using namespace std;
#define pb push_back
const int N = 2e5 + 5;
vector<int> g[N], h[N];
int sz[N], c[N], p[N];
bool vis[N], visC[N], er[N];
void dfssz(int s, int e = -1) {
sz[s] = 1;
for (auto u : g[s]) {
if (u == e || vis[u]) continue;
dfssz(u, s);
sz[s] += sz[u];
}
}
int centroid(int s, int n, int e = -1) {
for (auto u : g[s]) {
if (u == e || vis[u]) continue;
if (sz[u] > n/2) return centroid(u, n, s);
}
return s;
}
void dfsroot(int s, int e = -1) {
for (auto u : g[s]) {
if (u == e || vis[u]) continue;
p[u] = s;
dfsroot(u, s);
}
}
int ans = 1e9;
void solve(int R, int n) {
dfssz(R, n);
int nd = centroid(R, n);
dfsroot(nd);
// cout << R << ' ' << nd << ' ' << nd <<
if (!er[c[nd]]) {
queue<int> Q; Q.push(c[nd]);
vector<int> cl = {c[nd]};
visC[c[nd]] = 1;
bool ok = 1;
while (!Q.empty() && ok) {
int C = Q.front(); Q.pop();
for (auto u : h[C]) {
if (u == nd) continue;
int v = p[u];
while (!visC[c[v]]) {
if (er[c[v]]) {
ok = 0;
break;
}
visC[c[v]] = 1;
Q.push(c[v]);
cl.pb(c[v]);
v = p[v];
}
}
}
er[c[nd]] = 1;
for (auto i : cl) visC[i] = 0;
if (ok) ans = min(ans, (int)cl.size() - 1);
}
vis[nd] = 1;
for (auto u : g[nd]) {
if (vis[u]) continue;
solve(u, sz[u]);
}
}
int main() {
ios::sync_with_stdio(0);
cin.tie(0);
int n, k;
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];
h[c[i]].pb(i);
}
solve(1, n);
cout << ans << '\n';
}
