#include<bits/stdc++.h>
#define int long long
#define pb push_back
#define eb emplace_back
#define mp make_pair
#define F first
#define S second
#define vi vector<int>
#define pii pair<int,int>
using namespace std;
const int mxn = 2e5 + 5;
int n, k;
int c[mxn];
int sz[mxn];
int vis[mxn];
int isc[mxn];
int cvis[mxn];
int par[mxn];
int ans = 1e9;
vi adj[mxn];
vi visc;
vi cc;
vector<vi> colnode;
void get_sz(int node, int from){
sz[node] = 1;
for(auto u : adj[node]){
if(u != from && !vis[u]){
get_sz(u, node);
sz[node] += sz[u];
}
}
}
int get_centroid(int node, int from, int tar){
for(auto u : adj[node]){
if(u != from && !vis[u] && sz[u] > tar){
return get_centroid(u, node, tar);
}
}
return node;
}
void dfs(int node, int from){
par[node] = from;
cc.pb(node);
isc[node] = 1;
for(auto u : adj[node]){
if(u != from && !vis[u]){
dfs(u, node);
}
}
}
void centroid_decomp(int node){
get_sz(node, -1);
int ce =
get_centroid(node, -1, sz[node] / 2);
node = ce;
cc.clear();
dfs(node, -1);
queue<int> q;
q.push(node);
cvis[node] = 1;
int ct = 0;
vi cols;
bool ok = 1;
while(!q.empty()){
int cur = q.front();
q.pop();
if(!isc[cur]){
ok = 0;
break;
}
if(!visc[c[cur]]){
visc[c[cur]] = 1;
ct++;
cols.pb(c[cur]);
for(auto u : colnode[c[cur]]){
if(!cvis[u]){
if(isc[u]){
cvis[u] = 1;
}
else{
ok = 0;
break;
}
q.push(u);
}
}
}
if(!ok) break;
if(cur != ce){
cur = par[cur];
while(!cvis[cur]){
if(isc[cur]){
cvis[cur] = 1;
}
else{
ok = 0;
break;
}
q.push(cur);
cur = par[cur];
}
}
if(!ok) break;
}
if(ok){
ans = min(ans, ct);
}
for(auto u : cc){
isc[u] = 0;
cvis[u] = 0;
}
for(auto u : cols){
visc[u] = 0;
}
vis[ce] = 1;
for(auto u : adj[ce]){
if(!vis[u]){
centroid_decomp(u);
}
}
}
signed main(){
ios::sync_with_stdio(false);
cin.tie(NULL);
cin >> n >> k;
for(int i = 0; i < n - 1; i++){
int a, b;
cin >> a >> b;
a--;
b--;
adj[a].pb(b);
adj[b].pb(a);
}
for(int i = 0; i < n; i++){
cin >> c[i];
c[i]--;
colnode.pb({});
}
colnode.assign(k, {});
for(int i = 0; i < n; i++){
colnode[c[i]].pb(i);
}
visc.resize(k);
centroid_decomp(0);
cout << ans - 1;
}
