#include <bits/stdc++.h>
#ifdef __LOCAL__
#include <debug_local.h>
#endif
using namespace std;
const int mxN = 2e5 + 5;
vector<int> ad[mxN], l[mxN];
int city[mxN];
int ans = mxN;
int sz[mxN], par[mxN];
bool deleted[mxN], visc[mxN];
vector<int> vec;
void get_size(int u, int p = -1) {
vec.push_back(u);
visc[city[u]] = false;
sz[u] = 1;
for (int v : ad[u]) {
if (v == p || deleted[v]) continue;
get_size(v, u);
par[v] = u;
sz[u] += sz[v];
}
}
int get_centroid(int u, int p, int n) {
for (int v : ad[u]) {
if (v == p || deleted[v]) continue;
if (sz[v] > n / 2) return get_centroid(v, u, n);
}
return u;
}
void solve(int s) {
get_size(s);
int c = get_centroid(s, -1, sz[s]);
vec.clear();
get_size(c);
sort(vec.begin(), vec.end());
int cur = 0;
queue<int> q;
visc[city[c]] = true;
q.push(city[c]);
while (!q.empty()) {
cur++;
int u = q.front();
q.pop();
for (int v : l[u]) {
if (!binary_search(vec.begin(), vec.end(), v)) cur = mxN;
else {
if (v != c && !visc[city[par[v]]]) {
q.push(city[par[v]]);
visc[city[par[v]]] = true;
}
}
}
}
ans = min(ans, cur);
deleted[c] = true;
for (int v : ad[c]) {
if (!deleted[v]) solve(v);
}
}
void testCase() {
int n, k;
cin >> n >> k;
for (int i = 1; i < n; i++) {
int u, v;
cin >> u >> v;
ad[u].push_back(v);
ad[v].push_back(u);
}
for (int i = 1; i <= n; i++) {
cin >> city[i];
l[city[i]].push_back(i);
}
solve(1);
cout << ans - 1 << "\n";
}
int main() {
ios::sync_with_stdio(false);
cin.tie(nullptr);
testCase();
}
