#include<bits/stdc++.h>
#define ll long long
const int nmax = 2e5 + 5, N = 1e6;
const ll oo = 1e9 + 5, base = 311;
const int lg = 62, tx = 26;
const ll mod = 1e9 + 7, mod2 = 1e9+3;
#define pii pair<ll, ll>
#define fi first
#define se second
#define endl "\n"
#define debug(a, n) for(int i = 1; i <= n; ++i) cout << a[i] << ' '; cout << "\n";
#define NAME code
using namespace std;
int n, k;
vector<int> adj[nmax];
vector<int> mau[nmax];
int idx[nmax], c[nmax];
int sz[nmax], vis[nmax], cntw;
void dfs_1(int u, int p){
sz[u] = 1;
for(auto v : adj[u]){
if(vis[v] || v == p) continue;
dfs_1(v, u);
sz[u] += sz[v];
}
}
int Find(int u, int p){
for(auto v : adj[u]){
if(vis[v] || v == p) continue;
if(sz[v] > cntw / 2) return Find(v, u);
}
return u;
}
int rev[nmax], ok[nmax], par[nmax];
int res = 0;
void Init(int u, int p, int val){
ok[u] = val;
for(auto v : adj[u]){
if(vis[v] || v == p) continue;
par[v] = u;
Init(v, u, val);
}
}
struct holder{
int vis[nmax];
vector<int> tmp;
void add(int u){
vis[u] = 1;
tmp.push_back(u);
}
void clear(){
for(auto p : tmp) vis[p] = 0;
tmp.clear();
}
}one;
queue<int> q;
void solve(int u){
int root = u;
while(q.size()) q.pop();
for(auto p : mau[c[root]]){
if(!ok[p]){
res = oo;
return;
}
q.push(p);
one.add(p);
}
while(q.size()){
int u = q.front();q.pop();
if(u == root) continue;
int v = par[u];
// cout << u << ' ' << v << endl;
if(one.vis[v]) continue;
res++;
for(auto p : mau[c[v]]){
if(!ok[p]){
res = oo;
return;
}
q.push(p);
one.add(p);
}
}
}
int centroid(int u){
dfs_1(u, -1); cntw = sz[u];
int root = Find(u,-1);vis[root] = 1;
res = 0;
one.clear();
Init(root, -1, 1);
solve(root);
Init(root, -1, 0);
int cur = res;
for(auto v : adj[root]){
if(!vis[v])cur = min(cur, centroid(v));
}
return cur;
}
main(){
ios_base::sync_with_stdio(0);
cin.tie(0);cout.tie(0);
// freopen("code.inp", "r", stdin);
// freopen("code.out", "w", stdout);
cin >> n >> k;
for(int i = 1; i < n; ++i){
int u, v;
cin >> u >> v;
adj[u].push_back(v);
adj[v].push_back(u);
}
for(int i = 1; i <= n; ++i){
cin >> c[i];
mau[c[i]].push_back(i);
}
cout << centroid(1);
}
/*
7 3
3 2
1 3
7 3
5 2
6 2
4 7
2 1 3 1 2 3 2
*/
