#include <bits/stdc++.h>
using namespace std;
const int MX=2e5+5;
int N,K;
int A[MX],B[MX],S[MX];
vector<int> adj[MX],group[MX];
bool vis[MX], colVis[MX], subtree[MX], used[MX];
int sz[MX],par[MX];
int proc(int v) {
queue<int> q;
colVis[S[v]]=true;
int res=1;
for(auto u:group[S[v]]) {
if(!subtree[u]) return K;
vis[u]=true;
q.push(u);
}
while(!q.empty()) {
auto v=q.front(); q.pop();
if(!colVis[S[v]]) {
res+=1;
for(auto u:group[S[v]]) {
if(!subtree[u]) return K;
vis[u]=true;
q.push(u);
}
colVis[S[v]]=true;
}
if(par[v]!=0 && !vis[par[v]]) {
if(!subtree[par[v]]) return K;
vis[par[v]]=true;
q.push(par[v]);
}
}
return res;
}
int ans;
int getSize(int v, int p) {
sz[v]=1;
for(auto u:adj[v]) {
if(u==p || used[u]) continue;
sz[v]+=getSize(u,v);
}
return sz[v];
}
int getCen(int v, int p, int s) {
for(auto u:adj[v]) {
if(u==p || used[u]) continue;
if(2*sz[u]>s) return getCen(u,v,s);
}
return v;
}
vector<int> nodes;
void dfs(int v, int p) {
par[v]=p;
nodes.push_back(v);
for(auto u:adj[v]) {
if(u==p || used[u]) continue;
dfs(u,v);
}
}
void cdc(int v) {
int s=getSize(v,v);
int cen=getCen(v,v,s);
used[cen]=true;
nodes.push_back(cen);
par[cen]=0;
for(auto u:adj[cen]) {
if(used[u]) continue;
dfs(u,cen);
}
for(auto u:nodes) {
subtree[u]=true;
colVis[S[u]]=false;
vis[u]=false;
}
ans=min(ans,proc(cen));
for(auto u:nodes) {
subtree[u]=false;
colVis[S[u]]=false;
vis[u]=false;
}
nodes.clear();
for(auto u:adj[cen]) {
if(used[u]) continue;
cdc(u);
}
}
int main() {
cin.tie(0); ios_base::sync_with_stdio(0);
cin>>N>>K;
for(int i=0;i<N-1;i++) {
cin>>A[i]>>B[i];
adj[A[i]].push_back(B[i]);
adj[B[i]].push_back(A[i]);
}
for(int i=1;i<=N;i++) {
cin>>S[i];
group[S[i]].push_back(i);
}
ans=K;
cdc(1);
cout<<ans-1<<'\n';
}
