#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
typedef long long ll;
using namespace __gnu_pbds;
using namespace std;
template <typename T>
using ordered_set = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;
ll inf = 1e18;
ll ans = inf;
ll M = 200'010;
vector<vector<ll>> g(M);
vector<ll> city(M), par(M), sajz(M), cnt(M), have(M), seen(M), is_off(M);
vector<vector<ll>> S(M);
void sajz_dfs(ll v, ll p) {
sajz[v] =1;
par[v] = p;
for(auto u : g[v]) {
if(u==p || is_off[u]) continue;
sajz_dfs(u,v);
sajz[v] += sajz[u];
}
}
ll find_centroid(ll v, ll ts) {
for(auto u : g[v]) {
if(is_off[u]) continue;
if(u==par[v]) {
if(ts-sajz[v] > ts/2) return find_centroid(u,ts);
} else {
if(sajz[u] > ts/2) return find_centroid(u,ts);
}
}
return v;
}
void centroid_decomposition(ll v, ll ts) {
sajz_dfs(v,0);
v = find_centroid(v,ts);
sajz_dfs(v,0);
queue<pair<ll, ll>> Q;
Q.push({v,0});
vector<ll> used;
while(Q.size()) {
auto[dv,dp] = Q.front(); Q.pop();
used.push_back(city[dv]);
cnt[city[dv]]++;
for(auto u : g[dv]) {
if(is_off[u] || u==dp) continue;
Q.push({u,dv});
}
}
ll res = 0;
stack<ll> stos;
stos.push(city[v]);
while(stos.size()) {
ll x = stos.top(); stos.pop();
if(seen[x]) continue;
seen[x] = 1;
res++;
if(cnt[x]!=have[x]) {
res = inf;
break;
}
for(auto y : S[x]) {
if(is_off[par[y]]) continue;
stos.push(city[par[y]]);
}
}
for(auto x : used) {
seen[x] = 0;
cnt[x] = 0;
}
ans = min(ans, res);
is_off[v] = 1;
for(auto u : g[v]) {
if(is_off[u]) continue;
if(u==par[v]) centroid_decomposition(u, ts-sajz[v]);
else centroid_decomposition(u, sajz[u]);
}
}
int main() {
ios_base::sync_with_stdio(0);
cin.tie(0); cout.tie(0);
ll n, r;
cin >> n >> r;
for(ll i=1; i<n; ++i) {
ll a, b;
cin >> a >> b;
g[a].push_back(b);
g[b].push_back(a);
}
for(ll i=1; i<=n; ++i) {
cin >> city[i];
have[city[i]]++;
S[city[i]].push_back(i);
}
centroid_decomposition(1,n);
cout << ans-2 << "\n";
return 0;
}
