#include <bits/stdc++.h>
using namespace std;
#define int long long
#define FOR(i,a,b) for (int i = (a); i < (b); ++i)
#define pb push_back
#define all(a) a.begin(), a.end()
#define endl "\n"
void printVector(vector<int> a){
for (auto x: a) cout << x << " ";
cout << endl;
}
int min(int x, int y){
if (x < y) return x;
else return y;
}
vector<vector<int>> graph;
vector<int> subtree;
vector<int> vis;
int ans = 200000;
vector<int> overall;
int dp(int x, int p = -1){
if (vis[x]) return 0;
subtree[x] = 1;
for (auto item: graph[x]){
if (item == p) continue;
subtree[x] += dp(item, x);
}
return subtree[x];
}
int find_centroid(int x, int p, int n){
for (auto node: graph[x]){
if (node == p) continue;
if (!vis[node] && subtree[node]*2 > n) return find_centroid(node, x, n);
}
return x;
}
vector<int> par;
vector<vector<int>> o;
vector<int> done;
vector<int> b;
vector<int> col;
void setup(int x, int p = -1){
o[col[x]].pb(x);
b.pb(x);
for (auto node: graph[x]){
if (node == p) continue;
par[node] = x;
setup(node, x);
}
}
void init_centroid(int x = 1, int p = -1){
// cout << x << endl;
dp(x);
int c = find_centroid(x, -1, subtree[x]);
// cout << c << endl;
setup(c);
stack<int> s;
s.push(col[c]);
vector<int> e;
while (!s.empty()){
int current = s.top();
s.pop();
if (done[current]) continue;
e.pb(current);
for (auto item: o[current]){
if (col[par[item]] != col[item] && !done[col[par[item]]]) s.push(col[par[item]]);
}
done[current] = 1;
}
bool can = true;
for (auto item: e){
if (o[item].size() != overall[item]) can = false;
}
if (can){
// cout << c << e.size() << endl;
ans = min(ans, ((int)e.size()-1));
}
for (auto item: e){
o[item].clear();
done[item] = 0;
}
for (auto item: b) par[item] = -1;
b.clear();
vis[c] = 1;
for (auto node: graph[c]){
if (!vis[node]) init_centroid(node, c);
}
}
void solve(){
int n, k; cin >> n >> k;
graph.resize(n+1);
par.resize(n+1);
o.resize(k+1);
overall.resize(k+1);
done.resize(k+1);
subtree.resize(n+1);
vis.resize(n+1);
col.resize(n+1);
FOR(i,0,n-1){
int a, b; cin >> a >> b;
graph[a].pb(b);
graph[b].pb(a);
}
FOR(i,1,n+1){
cin >> col[i];
overall[col[i]]++;
}
init_centroid();
cout << ans << endl;
}
int32_t main(){
ios::sync_with_stdio(false);cin.tie(nullptr);
int t = 1; // cin >> t;
while (t--) solve();
}
