#include<bits/stdc++.h>
using namespace std;
#define F first
#define S second
#define endl '\n'
typedef long long ll;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
const int N = 2e5 + 50;
int n, k, c[N], sub[N], sz[N];
bool flg[N];
map<int, int> mp[N];
vector<int> adj[N];
vector<int> adjP[N], adjM[N];
int id[N], scz[N];
vector<int> vc;
bool vis[N];
void dfs(int u, int p) {
for (int v:adj[u]) {
if (v == p) continue;
dfs(v, u);
for (pii x:mp[v]) {
if (x.S < sz[x.F] && x.F != c[u]) {
adjP[x.F].push_back(c[u]);
adjM[c[u]].push_back(x.F);
}
mp[u][x.F] += x.S;
}
}
mp[u][c[u]]++;
}
void dfs2(int u) {
vis[u] = 1;
for (int v:adjP[u]) {
if (vis[v]) continue;
dfs2(v);
}
vc.push_back(u);
}
void sfd(int u) {
scz[id[u]]++;
for (int v:adjM[u]) {
if (id[v]) continue;
id[v] = id[u];
sfd(v);
}
}
void solve() {
cin >> n >> k;
for (int i = 1; i <= n-1; i++) {
int u, v;
cin >> u >> v;
adj[u].push_back(v);
adj[v].push_back(u);
}
for (int u = 1; u <= n; u++) {
cin >> c[u];
sz[c[u]]++;
}
dfs(1, 0);
for (int u = 1; u <= k; u++) {
sort(adjP[u].begin(), adjP[u].end());
adjP[u].resize(unique(adjP[u].begin(), adjP[u].end())-adjP[u].begin());
sort(adjM[u].begin(), adjM[u].end());
adjM[u].resize(unique(adjM[u].begin(), adjM[u].end())-adjM[u].begin());
}
for (int u = 1; u <= k; u++) {
if (!vis[u]) dfs2(u);
}
reverse(vc.begin(), vc.end());
for (int u:vc) {
if (!id[u]) {
flg[u] = 1;
id[u] = u;
sfd(u);
}
}
int ans = 1e9;
for (int u:vc) {
for (int v:adjP[u]) {
flg[id[u]] = flg[id[u]]&&(id[v] == id[u]);
}
}
for (int u:vc) {
if (flg[id[u]]) ans = min(ans, scz[id[u]]);
}
cout << ans-1 << endl;
}
int main() {
ios::sync_with_stdio(0), cin.tie(0), cout.tie(0);
solve();
return 0;
}
