/*************************************
* author: marvinthang *
* created: 05.12.2023 09:58:14 *
*************************************/
#include <bits/stdc++.h>
using namespace std;
#define fi first
#define se second
#define left ___left
#define right ___right
#define TIME (1.0 * clock() / CLOCKS_PER_SEC)
#define MASK(i) (1LL << (i))
#define BIT(x, i) ((x) >> (i) & 1)
#define __builtin_popcount __builtin_popcountll
#define ALL(v) (v).begin(), (v).end()
#define REP(i, n) for (int i = 0, _n = (n); i < _n; ++i)
#define REPD(i, n) for (int i = (n); i-- > 0; )
#define FOR(i, a, b) for (int i = (a), _b = (b); i < _b; ++i)
#define FORD(i, b, a) for (int i = (b), _a = (a); --i >= _a; )
#define FORE(i, a, b) for (int i = (a), _b = (b); i <= _b; ++i)
#define FORDE(i, b, a) for (int i = (b), _a = (a); i >= _a; --i)
#define scan_op(...) istream & operator >> (istream &in, __VA_ARGS__ &u)
#define print_op(...) ostream & operator << (ostream &out, const __VA_ARGS__ &u)
#ifdef LOCAL
#include "debug.h"
#else
#define file(name) if (fopen(name".inp", "r")) { freopen(name".inp", "r", stdin); freopen(name".out", "w", stdout); }
#define DB(...) 23
#define db(...) 23
#define debug(...) 23
#endif
template <class U, class V> scan_op(pair <U, V>) { return in >> u.first >> u.second; }
template <class T> scan_op(vector <T>) { for (size_t i = 0; i < u.size(); ++i) in >> u[i]; return in; }
template <class U, class V> print_op(pair <U, V>) { return out << '(' << u.first << ", " << u.second << ')'; }
template <size_t i, class T> ostream & print_tuple_utils(ostream &out, const T &tup) { if constexpr(i == tuple_size<T>::value) return out << ")"; else return print_tuple_utils<i + 1, T>(out << (i ? ", " : "(") << get<i>(tup), tup); }
template <class ...U> print_op(tuple<U...>) { return print_tuple_utils<0, tuple<U...>>(out, u); }
template <class Con, class = decltype(begin(declval<Con>()))> typename enable_if <!is_same<Con, string>::value, ostream&>::type operator << (ostream &out, const Con &con) { out << '{'; for (__typeof(con.begin()) it = con.begin(); it != con.end(); ++it) out << (it == con.begin() ? "" : ", ") << *it; return out << '}'; }
// end of template
void process(void) {
int n, k; cin >> n >> k;
vector <vector <int>> adj(n);
REP(i, n - 1) {
int u, v; cin >> u >> v; --u; --v;
adj[u].push_back(v);
adj[v].push_back(u);
}
vector <int> c(n);
vector <vector <int>> list_idx(k);
REP(i, n) {
cin >> c[i];
list_idx[--c[i]].push_back(i);
}
vector <bool> used(n), exist(k);
vector <int> sz(n), par(n), cnt(k);
function<void(int, int)> dfs_sz = [&] (int u, int par) {
sz[u] = 1;
exist[c[u]] = false;
cnt[c[u]] = 0;
for (int v: adj[u]) if (!used[v] && v != par) {
dfs_sz(v, u);
sz[u] += sz[v];
}
};
function<int(int, int, int)> find = [&] (int u, int par, int n) {
for (int v: adj[u]) if (!used[v] && v != par && sz[v] >= n / 2) return find(v, u, n);
return u;
};
int res = k - 1;
function<void(int)> solve = [&] (int u) {
dfs_sz(u, -1);
u = find(u, -1, sz[u]);
par[u] = -1;
function<void(int)> dfs = [&] (int u) {
++cnt[c[u]];
for (int v: adj[u]) if (!used[v] && v != par[u]) {
par[v] = u;
dfs(v);
}
};
dfs(u);
queue <int> q;
q.push(c[u]);
int cc = 0;
exist[c[u]] = true;
while (!q.empty()) {
int f = q.front(); q.pop();
if (cnt[f] != (int) list_idx[f].size()) {
cc = k;
break;
}
++cc;
for (int u: list_idx[f]) {
u = par[u];
if (u >= 0 && !exist[c[u]]) {
exist[c[u]] = true;
q.push(c[u]);
}
}
}
res = min(res, cc - 1);
used[u] = true;
for (int v: adj[u]) if (!used[v]) solve(v);
};
solve(0);
cout << res << '\n';
}
int main(void) {
ios_base::sync_with_stdio(false); cin.tie(nullptr); // cout.tie(nullptr);
file("JOI20_capital_city");
// int t; cin >> t; while (t--)
process();
// cerr << "Time elapsed: " << TIME << " s.\n";
return (0^0);
}
