/* nya */
#pragma GCC optimize("O4,unroll-loops,no-stack-protector")
#pragma GCC target("avx,avx2,sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,fma")
#include <bits/stdc++.h>
#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 Fors(i, a, b, s) for (int i = a; i <= b; i += s)
#define F first
#define S second
#define all(x) x.begin(), x.end()
#define sz(x) ((int)x.size())
#define eb emplace_back
#define int LL
#define INF (int)(1e18)
#define MOD (int)(1000000007)
// #define MOD (int)(998244353)
using namespace std;
using LL = long long;
// using LLL = __int128_t;
using pii = pair<int, int>;
#ifdef NYAOWO
#include "library/debug.hpp"
inline void USACO(const string &s) {
cerr << "USACO: " << s << "\n";
}
#else
#define debug(...)
inline void timer() {}
inline void USACO(const string &s) {
freopen((s + ".in").c_str(), "r", stdin);
freopen((s + ".out").c_str(), "w", stdout);
}
#endif
const int MAXN = 200020;
mt19937_64 rng(48763);
vector<int> adj[MAXN];
int vis[MAXN]; // -1 for expired nodes
int par[MAXN];
int ssz[MAXN];
int city[MAXN]; // town -> city
vector<int> town[MAXN]; // city -> towns
int vist[MAXN];
int dfs(int n, int p, int tag) {
vis[n] = tag;
par[n] = p;
int sz = 1;
for(auto &i:adj[n]) if(vis[i] != -1 && vis[i] != tag) {
sz += dfs(i, n, tag);
}
ssz[n] = sz;
return sz;
}
// {size, index}
pii cent(int n, int p, int N) {
pii res = {INF, -1};
int mx = 0;
for(auto &i:adj[n]) if(i != p && vis[i] >= 0) {
res = min(res, cent(i, n, N));
mx = max(mx, ssz[i]);
}
mx = max(mx, N - ssz[n]);
res = min(res, pii(mx, n));
return res;
}
int nya(int n, int siz) {
int tag = rng();
n = cent(n, n, siz).S;
dfs(n, n, tag);
queue<int> que;
int res = 0;
auto mark = [&](int t) {
// cout << "mark: " << t << "\n";
if(vis[t] != (~tag) && vis[t] != tag) return false;
while(vis[t] == tag) {
vis[t] = (~tag);
if(vist[city[t]] != tag) {
vist[city[t]] = tag;
que.emplace(city[t]);
}
if(t == n) break;
t = par[t];
}
return true;
};
mark(n);
while(!que.empty()) {
int c = que.front(); que.pop();
// cout << "city: " << c << "\n";
res++;
for(auto &i:town[c]) if(vis[i] != (~tag)) {
if(!mark(i)) {
res = INF;
break;
}
}
}
vis[n] = -1;
for(auto &i:adj[n]) if(vis[i] != -1) {
res = min(res, nya(i, dfs(i, i, rng())));
}
return res;
}
int32_t main() {
ios::sync_with_stdio(false);
cin.tie(0);
// OAO
int n, m; cin >> n >> m;
For(i, 1, n - 1) {
int a, b; cin >> a >> b;
adj[a].eb(b);
adj[b].eb(a);
}
For(i, 1, n) {
cin >> city[i];
town[city[i]].eb(i);
}
dfs(1, 1, 49);
cout << (nya(1, n) - 1) << "\n";
return 0;
}
