#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef long double ld;
#define pb push_back
#define mp make_pair
#define pii pair <int, int>
#define fast_io ios::sync_with_stdio(false);cin.tie(0);cout.tie(0);
#define F first
#define S second
const int maxn = 2e5 + 5;
vector <int> adj[maxn], vec[maxn];
int sz[maxn], par[maxn], c[maxn];
int ans = INT_MAX;
bool cent[maxn], mark[maxn], com[maxn], visit[maxn];
void dfs(int v, bool f, int p = -1){
sz[v] = 1;
com[v] = f;
for(int u : adj[v]){
if(!cent[u] && u != p){
dfs(u, f, v);
sz[v] += sz[u];
}
}
}
int find_centroid(int v, int s, int p = -1){
for(int u : adj[v]){
if(!cent[u] && u != p && sz[u] > s / 2){
return find_centroid(u, s, v);
}
}
return v;
}
void dfs2(int v, int p = -1){
for(int u : adj[v]){
if(!cent[u] && u != p){
par[u] = v;
dfs2(u, v);
}
}
}
void solve(int v){
dfs(v, 1);
int cn = find_centroid(v, sz[v]);
// cout << "cen : " << cn << endl;
par[cn] = -1;
dfs2(cn);
queue <int> q;
vector <int> vc;
q.push(c[cn]);
bool flag = true;
mark[c[cn]] = true;
while(q.size() && flag){
int x = q.front();
q.pop();
vc.pb(x);
if(visit[x])
flag = false;
for(int u : vec[x]){
if(!com[u])
flag = false;
if(par[u] != -1 && !mark[c[par[u]]]){
q.push(c[par[u]]);
mark[c[par[u]]] = true;
}
}
}
visit[c[cn]] = true;
if(flag){
ans = min(ans, (int)vc.size() - 1);
}
//clear
for(int u : vc)
mark[u] = false;
dfs(v, 0);
cent[cn] = true;
for(int u : adj[cn]){
if(!cent[u]){
solve(u);
}
}
}
int main(){
fast_io;
int n, k;
cin >> n >> k;
for(int i = 0; i < n - 1; i ++){
int x, y;
cin >> x >> y;
x --; y --;
adj[x].pb(y);
adj[y].pb(x);
}
for(int i = 0; i < n; i ++){
cin >> c[i];
vec[c[i]].pb(i);
}
ans = k - 1;
solve(0);
cout << ans;
return 0;
}
