#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
const int N = 2e5 + 7;
vector <int> g[N],gr[N],rg[N],t;
int c[N],sz[N],cmp[N],bad[N];
bool used[N],ok[N];
void add(int u, int v) {
gr[u].push_back(v);
rg[v].push_back(u);
}
int tin[N], tout[N];
int timer = 0;
void init(int u, int p) {
tin[u] = timer++;
for (auto v : g[u]) {
if (v != p) {
init(v, u);
}
}
tout[u] = timer++;
}
bool anc(int a, int b) {
return tin[a] <= tin[b] && tout[b] <= tout[a];
}
void dfs(int u, int p = -1) {
if (u != bad[c[u]]) {
add(c[u], c[p]);
}
for (auto v : g[u]) {
if (v != p) {
dfs(v, u);
}
}
}
void get_topsort(int u) {
used[u] = true;
for (auto v : gr[u]) {
if (!used[v]) {
get_topsort(v);
}
}
t.push_back(u);
}
int cnt = 0;
void jhfs(int u) {
used[u] = true;
cmp[u] = cnt;
++sz[cnt];
for (auto v : rg[u]) {
if (!used[v]) {
jhfs(v);
}
}
}
int main() {
ios_base::sync_with_stdio(false); cin.tie(0);
int n, k; cin >> n >> k;
for (int i = 0; i + 1 < n; ++i) {
int u, v;
cin >> u >> v;
--u, --v;
g[u].push_back(v);
g[v].push_back(u);
}
vector <vector <int>> who(k);
for (int i = 0; i < n; ++i) {
cin >> c[i];
--c[i];
who[c[i]].push_back(i);
}
init(0, -1);
for (int i = 0; i < k; ++i) {
int v = who[i].front();
for (auto w : who[i])
if (anc(w, v))
v = w;
bool ok = true;
for (auto w : who[i]) ok &= anc(v, w);
if (ok) bad[i] = v;
else bad[i] = -1;
}
dfs(0);
for (int i = 0; i < k; ++i) {
if (!used[i]) get_topsort(i);
}
reverse(t.begin(), t.end());
fill(used, used + k, false);
for (int u : t) {
if (!used[u]) {
jhfs(u);
++cnt;
}
}
fill(ok, ok + cnt, true);
for (int i = 0; i < k; ++i) {
for (int j : gr[i]) {
if (cmp[i] != cmp[j]) {
ok[cmp[i]] = false;
}
}
}
int ans = n;
for (int i = 0; i < cnt; ++i) {
if (ok[i]) ans = min(ans, sz[i]);
}
cout << ans - 1 << '\n';
}
