// ~~ icebear ~~
#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef pair<int, int> ii;
typedef pair<int, ii> iii;
template<class T>
bool minimize(T &a, const T &b) {
if (a > b) return a = b, true;
return false;
}
template<class T>
bool maximize(T &a, const T &b) {
if (a < b) return a = b, true;
return false;
}
#define FOR(i,a,b) for(int i=(a); i<=(b); ++i)
#define FORR(i,a,b) for(int i=(a); i>=(b); --i)
#define REP(i, n) for(int i=0; i<(n); ++i)
#define RED(i, n) for(int i=(n)-1; i>=0; --i)
#define MASK(i) (1LL << (i))
#define BIT(S, i) (((S) >> (i)) & 1)
#define mp make_pair
#define pb push_back
#define fi first
#define se second
#define all(x) x.begin(), x.end()
#define task "gen"
/*END OF TEMPLATE. ICEBEAR AND THE CAT WILL WIN VOI26 */
const int MOD = 1e9 + 7;
const int inf = 1e9 + 27092008;
const ll INF = 1e18 + 27092008;
const int N = 2e5 + 5;
int numNode, numCity;
vector<int> G[N], belong[N];
int sz[N], city[N], ans = inf;
bool isCentroid[N];
int get_sz(int u, int par) {
sz[u] = 1;
for(int v : G[u]) if (v != par && !isCentroid[v])
sz[u] += get_sz(v, u);
return sz[u];
}
int findCentroid(int u, int par, const int &subtree) {
for(int v : G[u]) if (v != par && !isCentroid[v] && sz[v] * 2 > subtree)
return findCentroid(v, u, subtree);
return u;
}
vector<int> nodes;
int cnt[N], par[N];
bool vis[N];
void dfs(int u) {
nodes.pb(u);
cnt[city[u]]++;
vis[u] = false;
for(int v : G[u]) if (v != par[u] && !isCentroid[v]) {
par[v] = u;
dfs(v);
}
}
bool haveAll(int city) {
return cnt[city] == (int)belong[city].size();
}
void buildCentroid(int u) {
int centroid = findCentroid(u, -1, get_sz(u, -1));
isCentroid[centroid] = true;
par[centroid] = -1;
dfs(centroid);
// cerr << "CENTROID : " << centroid << '\n';
if (haveAll(city[centroid])) {
queue<int> q;
int unite = 0;
for(int v : belong[city[centroid]]) {
q.push(v);
vis[v] = true;
}
while(!q.empty()) {
int x = q.front(); q.pop();
x = par[x];
if (x <= 0) continue;
// cout << x << ' ';
while(!vis[x]) {
if (haveAll(city[x]) == false) {
unite = inf;
break;
}
vis[x] = true;
for(int v : belong[city[x]]) if (!vis[v]) {
vis[v] = true;
q.push(v);
}
unite++;
}
if (unite == inf) break;
}
minimize(ans, unite);
}
// cerr << "\nDECOMPOSE : " << ans << '\n';
// exit(0);
for(int x : nodes) {
vis[x] = true;
cnt[city[x]]--;
}
nodes.clear();
for(int v : G[centroid]) if (!isCentroid[v])
buildCentroid(v);
}
void init(void) {
cin >> numNode >> numCity;
FOR(i, 2, numNode) {
int u, v;
cin >> u >> v;
G[u].pb(v);
G[v].pb(u);
}
FOR(i, 1, numNode) cin >> city[i], belong[city[i]].push_back(i);
}
void process(void) {
buildCentroid(1);
cout << ans;
}
int main() {
ios_base::sync_with_stdio(0);
cin.tie(0); cout.tie(0);
if (fopen(task".inp", "r")) {
freopen(task".inp", "r", stdin);
freopen(task".out", "w", stdout);
}
int tc = 1;
// cin >> tc;
while(tc--) {
init();
process();
}
return 0;
}
