// In the name of God
#include <bits/stdc++.h>
using namespace std;
#define F first
#define S second
#define PB push_back
#define MP make_pair
#define lc 2 * v
#define rc 2 * v + 1
#define mid (s + e) / 2
#define _sz(e) (int)e.size()
#define _all(e) e.begin() , e.end()
#define _lcm(a , b) (1ll * a * b) / __gcd(a , b)
#define ll long long
#define int long long
#define ld long double
#define pii pair <int , int>
#define pcc pair <char , char>
#define pll pair <long long , long long>
#define piii pair <int , pair <int , int>>
#define FAST ios::sync_with_stdio(0);cin.tie(0)
#pragma GCC optimize("Ofast")
// #pragma GCC target("ve,ve2,ve3,vse3,ve4,avmini,avmini2")
const int maxn = 3e5 + 10 , N = 2e5 + 10 , SQ = 320 , base = 800287 , mod = 1e9 + 7 , INF = 1e14 + 10 , lg = 22;
const ld eps = 1e-4;
int n , k , c[maxn] , res[maxn] , sz[maxn] , par[maxn];
bool death[maxn] , sub[maxn] , mark[maxn] , visited[maxn];
vector <int> edges[maxn] , town[maxn] , tmp;
void dfs_sz(int v , int p = -1) {
sz[v] = 1;
for (auto u : edges[v]) {
if(u != p && !death[u]) {
dfs_sz(u , v);
sz[v] += sz[u];
}
}
}
void dfs_sub(int v , int p = -1) {
sub[v] = 1 , par[v] = p , tmp.PB(v);
for (auto u : edges[v]) {
if(u != p && !death[u]) {
dfs_sub(u , v);
}
}
}
int find_centroid(int v , int tot , int p = -1) {
for (auto u : edges[v]) {
if(u != p && !death[u] && sz[u] > tot / 2) {
return find_centroid(u , tot , v);
}
}
return v;
}
void calc(int x) {
dfs_sub(x);
queue <int> q; q.push(x);
while(_sz(q)) {
int v = q.front(); q.pop();
if(visited[v]) {continue;}
visited[v] = 1 , tmp.PB(v);
if(!mark[c[v]]) {
for (auto u : town[c[v]]) {
if(!sub[u] || death[u]) {
res[x] = INF;
return ;
}
if(!visited[u]) {
q.push(u);
}
}
res[x]++;
mark[c[v]] = 1 , tmp.PB(c[v]);
}
if(par[v] != -1 && !visited[par[v]]) {
q.push(par[v]);
}
}
}
void centroid_tree() {
queue <int> q; dfs_sz(0);
q.push(find_centroid(0 , sz[0]));
while(_sz(q)) {
int v = q.front(); q.pop();
calc(v);
for (auto u : tmp) {
sub[u] = mark[u] = visited[u] = 0;
}
tmp.clear();
death[v] = 1;
for (auto u : edges[v]) {
if(!death[u]) {
dfs_sz(u);
q.push(find_centroid(u , sz[u]));
}
}
}
}
int32_t main() {
FAST;
cin >> n >> k;
for (int i = 0; i < n - 1; ++i) {
int x , y; cin >> x >> y;
x-- , y--;
edges[x].PB(y);
edges[y].PB(x);
}
for (int i = 0; i < n; ++i) {
cin >> c[i]; c[i]--;
town[c[i]].PB(i);
}
centroid_tree();
int ans = k - 1;
for (int i = 0; i < n; ++i) {
ans = min(ans , res[i] - 1);
}
cout << ans << '\n';
}
// Mistakes:
// * Read the problem carefully.
// * Check maxn.
// * Overflows.
