// In the name of God
#include<bits/stdc++.h>
using namespace std;
#define pb push_back
#define fi first
#define se second
#define mp make_pair
typedef long long ll;
const int N = 4e5 + 5, lg = 20;
int n, k;
int up[N][lg], f[N], c[N];
vector<int> adj[N], ver[N];
int h[N], tin[N], tout[N], T;
int par[N];
void dfs(int v, int p) {
par[v] = p;
up[v][0] = p;
for (int i = 1; i < lg; i++)
up[v][i] = up[up[v][i - 1]][i - 1];
tin[v] = ++T;
for (auto u : adj[v]) {
if (u != p) {
h[u] = h[v] + 1;
dfs(u, v);
}
}
tout[v] = T;
}
bool anc(int v, int u) {
return tin[v] <= tin[u] && tout[v] >= tout[u];
}
int lca(int v, int u) {
if (tin[v] > tin[u]) swap(v, u);
if (anc(v, u)) return v;
for (int i = lg - 1; i >= 0; i--)
if (!anc(up[u][i], v))
u = up[u][i];
return up[u][0];
}
vector<int> out[N], in[N];
void dfs2(int v, int p) {
int u = par[v];
while (h[u] > h[f[c[v]]]) {
out[c[v]].pb(c[u]);
in[c[u]].pb(c[v]);
u = par[u];
}
par[v] = u;
if (h[u] >= h[f[c[v]]]) {
out[c[v]].pb(c[f[c[v]]]);
in[c[f[c[v]]]].pb(c[v]);
par[v] = par[f[c[v]]];
}
for (auto u : adj[v]) {
if (u != p)
dfs2(u, v);
}
}
bool vis[N];
int col[N];
vector<int> vec;
void dfs3(int v) {
vis[v] = true;
for (auto u : out[v]) {
if (!vis[u]) dfs3(u);
}
vec.pb(v);
}
vector<int> V;
void dfs4(int v, int x) {
col[v] = x;
for (auto u : in[v]) {
if (!col[u])
dfs4(u, x);
}
V.pb(v);
}
void solve() {
cin >> n >> k;
for (int i = 0; i < n - 1; i++) {
int v, u; cin >> v >> u;
adj[v].pb(u);
adj[u].pb(v);
}
for (int i = 1; i <= n; i++) cin >> c[i], ver[c[i]].pb(i);
dfs(1, 0);
h[0] = -1;
tout[0] = T;
for (int i = 1; i <= k; i++) {
f[i] = ver[i].back();
for (auto v : ver[i])
f[i] = lca(f[i], v);
}
dfs2(1, 0);
for (int i = 1; i <= k; i++) {
if (!vis[i])
dfs3(i);
}
int ans = n + 1;
for (int i = k - 1; i >= 0; i--) {
int w = vec[i];
if (col[w] == 0) {
V.clear();
dfs4(w, w);
bool ok = true;
int cnt = V.size();
for (auto v : V) {
for (auto u : out[v])
ok &= col[u] == col[v];
}
if (ok) ans = min(ans, cnt);
}
}
cout << ans - 1 << '\n';
}
int32_t main() {
ios::sync_with_stdio(0), cin.tie(0), cout.tie(0);
int tc = 1; // cin >> tc;
while (tc--) {
solve();
}
return 0;
}
