// File AA.cpp created on 13.08.2025 at 11:06:04
#include <bits/stdc++.h>
using i64 = long long;
#ifdef DEBUG
#include "/home/ahmetalp/Desktop/Workplace/debug.h"
#else
#define debug(...) void(23)
#endif
int main() {
std::ios::sync_with_stdio(false);
std::cin.tie(nullptr);
int N, K;
std::cin >> N >> K;
std::vector<std::vector<int>> adj(N);
for (int i = 1; i < N; ++i) {
int A, B;
std::cin >> A >> B;
--A, --B;
adj[A].emplace_back(B);
adj[B].emplace_back(A);
}
std::vector<std::vector<int>> cols(K);
std::vector<int> colscnt(K);
std::vector<int> C(N);
for (int i = 0; i < N; ++i) {
std::cin >> C[i];
--C[i];
cols[C[i]].emplace_back(i);
}
std::vector<int> siz(N), act(N, true), vis(N, false), par(N);
auto calc_sizes = [&](auto&& self, int v, int pr) -> void {
siz[v] = 1;
for (auto u : adj[v]) {
if (u == pr || !act[v]) {
continue;
}
self(self, u, v);
siz[v] += siz[u];
}
};
auto find_centro = [&](auto&& self, int v, int pr, int gs) -> int {
for (auto u : adj[v]) {
if (u == pr || !act[v]) {
continue;
}
if (siz[u] * 2 > gs) {
return self(self, u, v, gs);
}
}
return v;
};
int ans = K + 1;
std::vector<int> vtx;
auto dfs = [&](auto&& self, int v, int pr) -> void {
par[v] = pr;
vtx.emplace_back(v);
for (auto u : adj[v]) {
if (u == pr || !act[u]) {
continue;
}
self(self, u, v);
}
};
auto dnq = [&](auto&& self, int v) -> void {
calc_sizes(calc_sizes, v, v);
v = find_centro(find_centro, v, v, siz[v]);
vtx.clear();
dfs(dfs, v, v);
for (auto u : vtx) {
vis[u] = false;
colscnt[C[u]]++;
}
if (colscnt[C[v]] == cols[C[v]].size()) {
int cnt = 1;
std::vector<int> stk;
for (auto u : cols[C[v]]) {
assert(vis[u] == false);
vis[u] = true;
stk.emplace_back(u);
}
while (!stk.empty()) {
auto u = stk.back();
stk.pop_back();
u = par[u];
while (!vis[u]) {
if (colscnt[C[u]] != cols[C[u]].size()) {
cnt = K + 1;
break;
}
for (auto w : cols[C[u]]) {
assert(vis[w] == false);
vis[w] = true;
stk.emplace_back(w);
}
cnt++;
u = par[u];
}
if (cnt == K + 1) {
break;
}
}
ans = std::min(ans, cnt);
}
for (auto u : vtx) {
colscnt[C[u]]--;
}
#ifdef LOCAL
assert(std::count(colscnt.begin(), colscnt.end(), 0) == K);
#endif
act[v] = false;
for (auto u : adj[v]) {
if (!act[u]) {
continue;
}
self(self, u);
}
};
dnq(dnq, 0);
std::cout << ans - 1 << '\n';
return 0;
}
