#include <iostream>
#include <vector>
#include <algorithm>
#include <cassert>
#include <set>
using ll = long long;
#define debug(x) #x << " = " << x << '\n'
const int INF = 1e9;
int main() {
std::ios_base::sync_with_stdio(false);
std::cin.tie(0);
int n, k;
std::cin >> n >> k;
std::vector<std::vector<int>> g(n);
for (int i = 1; i < n; i++) {
int u, v;
std::cin >> u >> v;
u--, v--;
g[u].push_back(v);
g[v].push_back(u);
}
std::vector<int> c(n);
for (int &x : c) {
std::cin >> x;
x--;
}
std::vector<bool> blocked(n, false);
std::vector<int> sz(n);
auto calc_sizes = [&](auto &&self, int u, int p) -> void {
sz[u] = 1;
for (int v : g[u]) {
if (v != p && !blocked[v]) {
self(self, v, u);
sz[u] += sz[v];
}
}
};
auto find_centroid = [&](auto &&self, int u, int p, int tsz) -> int {
for (int v : g[u]) {
if (v != p && !blocked[v] && sz[v] * 2 > tsz) {
return self(self, v, u, tsz);
}
}
return u;
};
std::vector<bool> blockedcolor(k, false);
std::vector<int> parent(n);
std::vector<int> vertices;
auto calc_dfs = [&](auto &&self, int u) -> void {
vertices.push_back(u);
for (int v : g[u]) {
if (v != parent[u] && !blocked[v]) {
parent[v] = u;
self(self, v);
}
}
};
std::vector<bool> vis(n, false);
std::vector<bool> inSubtree(n, false);
std::vector<std::vector<int>> thisColor(k);
for (int i = 0; i < n; i++) {
thisColor[c[i]].push_back(i);
}
std::vector<int> f(k, 0);
int answer = k - 1;
auto build_decomp = [&](auto &&self, int u) -> void {
calc_sizes(calc_sizes, u, -1);
int centroid = find_centroid(find_centroid, u, -1, sz[u]);
parent[centroid] = -1;
calc_dfs(calc_dfs, centroid);
if (!blockedcolor[c[centroid]]) {
std::vector<int> st;
std::vector<int> st2;
for (int u : vertices) {
f[c[u]]++;
inSubtree[u] = true;
}
int cur = 0;
if (f[c[centroid]] < (int) thisColor[c[centroid]].size()) {
cur = 1e9;
} else {
for (int u : thisColor[c[centroid]]) {
st.push_back(u);
vis[u] = true;
}
}
while (!st.empty() && cur < answer) {
int u = st.back();
st2.push_back(u);
st.pop_back();
if (parent[u] != -1 && !vis[parent[u]]) {
cur++;
if (f[c[parent[u]]] < (int) thisColor[c[parent[u]]].size()) {
cur = 1e9;
} else {
for (int v : thisColor[c[parent[u]]]) {
vis[v] = true;
st.push_back(v);
}
}
}
}
for (int x : st) {
vis[x] = false;
}
for (int x : st2) {
if (!inSubtree[x]) {
cur = 1e9;
}
vis[x] = false;
}
answer = std::min(answer, cur);
for (int x : vertices) {
inSubtree[x] = false;
f[c[x]]--;
}
}
blocked[centroid] = true;
blockedcolor[c[centroid]] = true;
vertices.clear();
for (int v : g[centroid]) {
if (!blocked[v]) {
self(self, v);
}
}
};
build_decomp(build_decomp, 0);
std::cout << answer;
return 0;
}
