#include <iostream>
#include <vector>
#include <set>
#include <algorithm>
using namespace std;
const int N = 1<<18;
vector<int> nei[N], adj[N], jda[N], lst[N], scc, ord;
int pr[N], ch[N], col[N], id[N], num[N], tp[N], lca[N], vis[N], cur;
void dfs1(int u){
ch[u] = 1;
for (int &i : nei[u]){
nei[i].erase(find(begin(nei[i]), end(nei[i]), u));
dfs1(i);
pr[i] = u;
ch[u] += ch[i];
if (ch[i] > ch[nei[u][0]])
swap(nei[u][0], i);
}
}
void dfs2(int u, int t){
num[u] = ++cur;
tp[u] = t;
for (int i : nei[u])
dfs2(i, (i == nei[u][0] ? t : i));
}
int LCA(int u, int v){
for (; tp[u] != tp[v]; v = pr[tp[v]]){
if (num[v] < num[u])
swap(u, v);
}
if (num[v] < num[u])
swap(u, v);
return u;
}
void dfs3(int u){
int v = u;
while (1){
adj[u].push_back(v);
jda[v].push_back(u);
if (v == lca[col[u]])
break;
v = pr[v];
}
for (int i : nei[u])
dfs3(i);
}
void dfs4(int u){
vis[u] = 1;
for (int i : adj[u])
if (vis[i] != 1)
dfs4(i);
ord.push_back(u);
}
void dfs5(int u){
vis[u] = 2;
scc.push_back(u);
id[u] = cur;
for (int i : jda[u])
if (vis[i] != 2)
dfs5(i);
}
int main(){
int n, k;
cin>>n>>k;
for (int i=1;i<n;i++){
int a, b;
cin>>a>>b;
nei[a].push_back(b);
nei[b].push_back(a);
}
dfs1(1);
dfs2(1, 1);
for (int i=1;i<=n;i++){
cin>>col[i];
lst[col[i]].push_back(i);
if (lca[col[i]] == 0)
lca[col[i]] = i;
else
lca[col[i]] = LCA(i, lca[col[i]]);
}
for (int i=1;i<=k;i++){
int L = lst[i].back();
for (int j : lst[i]){
adj[L].push_back(j);
jda[j].push_back(L);
L = j;
}
}
dfs3(1);
for (int i=1;i<=n;i++)
if (vis[i] == 0)
dfs4(i);
int ans = n;
while (ord.size() > 0){
int u = ord.back(); ord.pop_back();
if (vis[u] != 2){
++cur;
scc = {};
dfs5(u);
set<int> st;
bool t = 1;
for (int i : scc){
for (int j : adj[i]){
if (id[j] != cur)
t = 0;
}
st.insert(col[i]);
}
if (t)
ans = min(ans, (int)st.size());
}
}
cout<<ans - 1<<endl;
}
