#include <bits/stdc++.h>
#pragma GCC optimize("O3,unroll-loops")
#pragma GCC target("avx2")
//#define int long long
#define pii pair<int,int>
#define vi vector<int>
#define ff first
#define ss second
#define sp << " " <<
#define all(x) x.begin(),x.end()
#define big(x) ((int)(x.size()))
using namespace std;
const int MOD = 1e9+7, LIM = 1e9, inf = 2e9,MAXN = 1e6+1;
const int N = 2e5+1;
vi edges[N];
int sz[N],dead[N],mark[N],col[N],par[N];
int ans = inf;
int marker = 0;
int szs(int node,int p) {
sz[node] = 1;
for (auto it : edges[node]) if (it != p && !dead[it]) sz[node]+=szs(it,node);
return sz[node];
}
int centro(int node,int p,int s) {
for (auto it : edges[node]) {
if (it == p || dead[it]) continue;
if (sz[it]*2 > s) return centro(it,node,s);
}
return node;
}
void dfs(int node,int p) {
mark[node] = marker;
par[node] = p;
for (auto it : edges[node]) {
if (dead[it] || it == p) continue;
dfs(it,node);
}
}
vi whohas[N];
vi pshd;
vi done(N,0);
vi touched(N,0);
vi toca;
void decompose(int node) {
++marker;
int s = szs(node,node);
int r = centro(node,node,s);
dfs(r,r);
queue<int> q;
bool cool = 1;
for (auto it : whohas[col[r]]) {
if (mark[it] != marker) {
cool = 0;
break;
}
q.push(it);
}
done[col[r]] = 1;
pshd.push_back(col[r]);
int hadtodo = 1;
while (!q.empty() && cool && hadtodo <= ans) {
int f = q.front();
q.pop();
while (f != r && !touched[f]) {
touched[f] = 1;
toca.push_back(f);
if (!done[col[f]]) {
done[col[f]] = 1;
pshd.push_back(col[f]);
hadtodo++;
if (hadtodo > ans) break;
for (auto it : whohas[col[f]]) {
if (mark[it] != marker) {
cool = 0;
break;
}
q.push(it);
}
}
f = par[f];
}
}
if (cool) ans = min(ans,hadtodo-1);
dead[r] = 1;
for (auto it : pshd) done[it] = 0;
pshd.clear();
for (auto it : toca) touched[it] = 0;
toca.clear();
for (auto it : edges[r]) if (!dead[it]) decompose(it);
}
void solve() {
int n,k;
cin >> n >> k;
for (int i=1;i<n;i++) {
int a,b;
cin >> a >> b;
edges[a].push_back(b);
edges[b].push_back(a);
}
for (int i=1;i<=n;i++) cin >> col[i];
for (int i=1;i<=n;i++) whohas[col[i]].push_back(i);
decompose(1);
cout << ans << '\n';
}
signed main() {
ios_base::sync_with_stdio(0); cin.tie(0);
#ifdef Dodi
freopen("in.txt", "r", stdin);
freopen("out.txt", "w", stdout);
#endif
int t = 1;
//cin >> t;
while (t --> 0) solve();
}
