#include "bits/stdc++.h"
using namespace std;
#define int long long
#define double long double
const int MAXN = 5e5 + 10;
const int MOD = 1e9 + 7;
mt19937_64 rng((int)std::chrono::steady_clock::now().time_since_epoch().count());
int rnd(int x, int y) {
int u = uniform_int_distribution<int>(x, y)(rng); return u;
}
int bm(int b, int p) {
if(p==0) return 1 % MOD;
int r = bm(b, p >> 1);
if(p&1) return (((r*r) % MOD) * b) % MOD;
return (r*r) % MOD;
}
int inv(int b) {
return bm(b, MOD-2);
}
int fastlog(int x) {
return (x == 0 ? -1 : 64 - __builtin_clzll(x) - 1);
}
void printcase(int i) { cout << "Case #" << i << ": "; }
static void run_with_stack_size(void (*func)(void), size_t stsize) {
char *stack, *send;
stack = (char *)malloc(stsize);
send = stack + stsize - 16;
send = (char *)((uintptr_t)send / 16 * 16);
asm volatile(
"mov %%rsp, (%0)\n"
"mov %0, %%rsp\n"
:
: "r"(send));
func();
asm volatile("mov (%0), %%rsp\n" : : "r"(send));
free(stack);
}
int n, k;
int c[MAXN], sz[MAXN];
vector<int> tr[MAXN];
vector<int> adj[MAXN], rev[MAXN];
stack<int> ts;
bool vis[MAXN];
void dfs1(int node) {
vis[node] = 1;
for(int x: adj[node]) {
if(!vis[x]) dfs1(x);
}
ts.push(node);
}
vector<int> comp;
vector<int> cond[MAXN];
int dsu[MAXN];
int set_of(int u) {
if(dsu[u] == u) return u;
return dsu[u] = set_of(dsu[u]);
}
void union_(int u, int v) {
dsu[set_of(u)] = set_of(v);
}
void dfs2(int node) {
vis[node] = 1;
for(int x: rev[node]) {
if(!vis[x]) {
dfs2(x);
}
}
comp.push_back(node);
}
int tin[MAXN], cur;
void dfs0(int node, int prv) {
tin[node] = ++cur;
sz[node] = 1;
for(int x: tr[node]) {
if(x != prv) {
dfs0(x, node);
sz[node] += sz[x];
}
}
}
set<int> city[MAXN];
bool have(int node, int prv, int tar) {
if(tin[node] < tin[prv]) {
if(*city[tar].rbegin() >= tin[prv] + sz[prv]) return 1;
if(*city[tar].begin() < tin[prv]) return 1;
return 0;
}
else {
// [tin[node], tin[node] + sz[node])
auto it = city[tar].lower_bound(tin[node]);
if(it != city[tar].end() && (*it) < tin[node] + sz[node]) return 1;
return 0;
}
return 0;
}
void solve(int tc) {
cin >> n >> k;
vector<pair<int,int> > edges;
for(int i=1; i<n; i++) {
int u, v;
cin >> u >> v;
edges.push_back({u, v});
tr[u].push_back(v);
tr[v].push_back(u);
}
for(int i=1; i<=n; i++) {
cin >> c[i];
}
dfs0(1, -1);
for(int i=1; i<=n; i++) {
city[c[i]].insert(tin[i]);
}
for(pair<int, int> k : edges) {
if(have(k.first, k.second, c[k.second])) {
adj[c[k.second]].push_back(c[k.first]);
}
if(have(k.second, k.first, c[k.first])) {
adj[c[k.first]].push_back(c[k.second]);
}
}
for(int i=1; i<=k; i++) {
for(int x: adj[i]) {
rev[x].push_back(i);
}
}
for(int i=1; i<=k; i++) {
if(!vis[i]) {
dfs1(i);
}
}
for(int i=1; i<=k; i++) vis[i] = 0, dsu[i] = i;
while(ts.size()) {
int tp = ts.top();
ts.pop();
if(!vis[tp]) {
comp.clear();
dfs2(tp);
for(int i=1; i<comp.size(); i++) {
union_(comp[i-1], comp[i]);
}
}
}
set<pair<int,int>> newedges;
for(int i=1; i<=k; i++) {
for(int x: adj[i]) {
if(set_of(i) != set_of(x) && !newedges.count({set_of(i), set_of(x)})) {
cond[set_of(i)].push_back(set_of(x));
newedges.insert({set_of(i), set_of(x)});
}
}
}
int ans = 1e9;
int cnt[k+1];
for(int i=1; i<=k; i++) {
cnt[i] = 0;
}
for(int i=1; i<=k; i++) {
cnt[set_of(i)]++;
}
for(int i=1; i<=k; i++) {
if(set_of(i) == i && cond[i].empty()) {
ans = min(ans, cnt[i]);
}
}
cout << ans - 1 << "\n";
}
void uwu() {
ios::sync_with_stdio(0); cin.tie(0);
int t = 1; //cin >> t;
for(int i=1; i<=t; i++) solve(i);
}
int32_t main() {
#ifdef ONLINE_JUDGE
uwu();
#endif
#ifndef ONLINE_JUDGE
run_with_stack_size(uwu, 1024 * 1024 * 1024); // run with a 1 GiB stack
#endif
}
/*
g++ A.cpp -std=c++17 -O2 -o A
./A < input.txt
*/
