#include <bits/stdc++.h>
using namespace std;
#define ii pair<int, int>
#define fi first
#define se second
#define pb push_back
#define eb emplace_back
const int N = 2e5 + 5;
int n, k;
vector<int> ad[N], in[N];
int col[N];
ii ed[N];
int sz[N], dd[N], cnt, cnt_col[N], pd[N], vis[N];
int vis_col[N];
int res = 1e9;
void find_size(int u, int par) {
sz[u] = 1;
cnt++;
for (int &v : ad[u]) {
if(v != par && !dd[v]) {
find_size(v, u);
sz[u] += sz[v];
//cerr << sz[v] << '\n';
}
}
}
int find_big(int u, int par) {
for (int &v : ad[u]) {
if(v != par && !dd[v] && sz[v] >= cnt / 2) {
return find_big(v, u);
}
}
return u;
}
void cen(int u) {
cnt = 0;
find_size(u, 0);
u = find_big(u, 0);
//cerr << u << ' ';
int root = u;
pd[u] = u;
function<void(int, int)> dfs = [&](int u, int par) {
vis[u] = root;
for (auto v : ad[u]) {
if(v != par && !dd[v]) {
pd[v] = u;
vis[v] = root;
dfs(v, u);
}
}
};
dfs(u, 0);
vector <int> ans;
queue <int> q;
q.push(u);
int dem = -1;
bool ok = 1;
while(q.size() && ok) {
int u = q.front();
q.pop();
dem++;
while(ok) {
if(vis[u] == 0) break;
if(vis_col[col[u]] == 0) {
dem -= cnt_col[col[u]];
ans.pb(col[u]);
vis_col[col[u]] = 1;
for (int &v : in[col[u]]) {
q.push(v);
if(vis[v] != root) {
ok = 0;
break;
}
}
}
vis[u] = 0;
u = pd[u];
if(u == root) break;
}
}
for (auto v : ans) vis_col[v] = 0;
if(dem == 0) {
res = min(res, (int)(ans.size()) - 1);
}
dd[u] = 1;
for (auto v : ad[u]) {
if(!dd[v]) {
cen(v);
}
}
}
int32_t main() {
ios_base::sync_with_stdio(false);
cin.tie(0); cout.tie(0);
cin >> n >> k;
for (int i = 1; i < n; ++i) {
int u, v;
cin >> u >> v;
ed[i] = {u, v};
ad[u].pb(v);
ad[v].pb(u);
}
for (int i = 1; i <= n; ++i) {
cin >> col[i];
cnt_col[col[i]]++;
in[col[i]].pb(i);
}
cen(1);
cout << res << '\n';
}
