#include "bits/stdc++.h"
using namespace std;
const int INF = 0x3f3f3f3f;
int k, ans = INF;
vector< vector<int> > g, towns;
vector<int> c, sz, par, cur;
vector<bool> used;
void dfs(int u, int p, vector<int> &out) {
sz[u] = 1; par[u] = p;
out.push_back(u);
for (auto& v : g[u]) {
if (v != p && !used[v]) {
dfs(v, u, out);
sz[u] += sz[v];
}
}
}
int find_centroid(int u, int p, int n) {
for (auto& v : g[u]) {
if (v != p && sz[v] > n / 2 && !used[v]) {
return find_centroid(v, u, n);
}
}
return u;
}
void solve(int u) {
vector<int> junk;
dfs(u, -1, junk);
int centroid = find_centroid(u, -1, sz[u]);
dfs(centroid, -1, cur);
map<int, int> cnt;
for (auto& x : cur) {
cnt[c[x]]++;
}
set<int> st;
if (cnt[c[centroid]] == (int) towns[c[centroid]].size()) {
bool pos = true;
queue<int> q;
for (auto& x : towns[c[centroid]]) {
q.push(x);
}
st.insert(c[centroid]);
while (!q.empty()) {
int x = q.front(); q.pop();
if (x != centroid && !st.count(c[par[x]])) {
if (cnt[c[par[x]]] != (int) towns[c[par[x]]].size()) {
pos = false;
break;
}
for (auto& y : towns[c[par[x]]]) {
q.push(y);
}
st.insert(c[par[x]]);
}
}
if (pos) {
ans = min(ans, (int) st.size());
}
}
used[centroid] = true;
cur.clear();
for (auto& v : g[centroid]) {
if (!used[v]) {
solve(v);
}
}
}
int main() {
ios::sync_with_stdio(false);
cin.tie(0);
int n;
cin >> n >> k;
g.resize(n + 1);
for (int i = 0; i < n - 1; i++) {
int a, b;
cin >> a >> b;
g[a].push_back(b);
g[b].push_back(a);
}
c.resize(n + 1);
towns.resize(k + 1);
for (int i = 1; i <= n; i++) {
cin >> c[i];
towns[c[i]].push_back(i);
}
par.resize(n + 1);
sz.resize(n + 1);
used.assign(n + 1, false);
solve(1);
cout << ans - 1 << '\n';
return 0;
}
