// https://oj.uz/submission/954992
#include <bits/stdc++.h>
using namespace std;
const int N = 200008;
int n, k, cnt = 0, bl[N] /* block */, a[N], c[N], vis[N], g[N], ans = (int) 1e18, par[N], sz[N];
vector<int> adj[N], vt[N];
void dfs_sz(int u, int p) {
bl[u] = cnt;
sz[u] = 1;
for (int v : adj[u]) {
if (v == p || c[v]) continue;
dfs_sz(v, u);
sz[u] += sz[v];
}
}
int find(int u, int p, int tot) {
int mx = -1, ret = -1;
for (int v : adj[u]) {
if (v == p || c[v]) continue;
ret = max(ret, find(v, u, tot));
mx = max(mx, sz[v]);
}
mx = max(mx, tot - sz[u]);
if (mx <= tot / 2) return u;
return ret;
}
void dfs_par(int u, int p) {
for (int v : adj[u]) {
if (v == p || c[v]) continue;
dfs_par(v, u);
par[v] = u;
}
}
void solve(int u) {
int cur = 0;
++cnt;
dfs_sz(u, -1);
int cent = find(u, -1, sz[u]);
c[cent] = 1;
dfs_par(cent, -1);
queue<int> q;
bool ok = 1;
g[a[cent]] = cnt;
q.push(a[cent]);
while (!q.empty()) {
auto node = q.front();
q.pop();
cur++;
for (int v : vt[node]) {
if (bl[v] != cnt) {
ok = 0;
break;
}
int x = v;
while (vis[x] != cnt) {
if (g[a[x]] != cnt) {
g[a[x]] = cnt;
q.push(a[x]);
}
vis[x] = cnt;
if (x == cent) break;
x = par[x];
}
}
if (!ok) break;
}
if (ok) ans = min(ans, cur);
for (int v : adj[cent]) if (!c[v]) solve(v);
}
int main() {
ios::sync_with_stdio(0); cin.tie(0);
cin >> n >> k;
for (int i = 1; i < n; i++) {
int u, v;
cin >> u >> v;
adj[u].push_back(v);
adj[v].push_back(u);
}
for (int i = 1; i <= n; i++) {
g[i] = vis[i] = -1;
cin >> a[i];
vt[a[i]].push_back(i);
}
solve(1);
cout << ans - 1 << '\n';
}
