#include <bits/stdc++.h>
#define int long long
using namespace std;
int a,k;
vector <int> z[1000005];
int t[1000005];
int child[1000005];
int del[1000005];
int sz;
int mark[1000005];
int cur;
vector <int> col[1000005];
int up[1000005];
int min1=1e9;
bool vis[1000005];
bool viscol[1000005];
void predfs(int i,int par){
child[i]=1;
for (auto p:z[i]){
if (p==par || del[p]){
continue;
}
predfs(p,i);
child[i]+=child[p];
}
}
int centroid(int i,int par){
for (auto p:z[i]){
if (p==par || del[p]){
continue;
}
if (child[p]>sz/2){
return centroid(p,i);
}
}
return i;
}
void dfs1(int i,int par){
mark[i]=cur;
up[i]=par;
for (auto p:z[i]){
if (p==par|| del[p]){
continue;
}
dfs1(p,i);
}
}
void decompose(int i){
predfs(i,0);
sz=child[i];
int u=centroid(i,0);
for (int i=1;i<=a;i++){
vis[i]=true;
viscol[i]=true;
}
vis[u]=false;
viscol[t[u]]=false;
cur++;
dfs1(u,0);
bool check=true;
queue<int> q;
q.push(t[u]);
int res=0;
while (q.size()){
int pos=q.front();
res++;
q.pop();
for (auto p:col[pos]){
// cout << p << "\n";
if (mark[p]!=cur){
check=false;
break;
}
int t1=p;
while (vis[t1]){
if (viscol[t[t1]]){
q.push(t[t1]);
viscol[t[t1]]=false;
}
vis[t1]=false;
t1=up[t1];
}
}
}
if (check){
min1=min(min1,res-1);
}
del[u]=1;
// cout << u << " " << check << " " << res << "\n";
for (auto p:z[u]){
if (del[p]){
continue;
}
// decompose(p);
}
}
signed main()
{
ios_base::sync_with_stdio(false);
cin.tie(NULL);
cin >> a >> k;
for (int i=1;i<a;i++){
int x,y;
cin >> x >> y;
z[x].push_back(y);
z[y].push_back(x);
}
for (int i=1;i<=a;i++){
cin >> t[i];
col[t[i]].push_back(i);
}
// cout << "\n";
decompose(1);
cout << min1 << "\n";
return 0;
}
