#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef vector<int> vi;
#define pb push_back
#define sz(x) (int)(x).size()
void ckmin(int& a, int b){
a = min(a, b);
}
const int MOD = 1e9+7;
#include <ext/pb_ds/assoc_container.hpp>
using namespace __gnu_pbds;
template<class T> using Tree = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;
struct HashFunc{
size_t operator()(ll a){
return ((a+123485122314LL)^((a+14123901283002LL)>>30));
}
};
gp_hash_table<ll, vi> g;
const int mx = 200005;
vi adj[mx];
int C[mx];
vi invC[mx];
int ans = MOD;
bool done[mx];
int sub[mx];
void genSub(int node, int p = -1){
sub[node] = 1;
for(auto u: adj[node]){
if(done[u]) continue;
if(u == p) continue;
genSub(u, node);
sub[node]+=sub[u];
}
}
bool in_subtree[mx];
bool comp_inc[mx];
void setInSubtree(int node, bool val, int p = -1){
in_subtree[node] = val;
for(auto u: adj[node]){
if(done[u]) continue;
if(u == p) continue;
setInSubtree(u, val, node);
}
}
int par[mx];
void genPar(int node, int p = -1){
par[node] = p;
for(auto u: adj[node]){
if(done[u]) continue;
if(u == p) continue;
genPar(u, node);
}
}
void centroidDecomp(int node){
// cout << "centroidDecomp: " << node << "\n";
// cout.flush();
genSub(node);
int cen = node;
int p = -1;
while(true){
bool found = 0;
for(auto u: adj[cen]){
if(done[u]) continue;
if(u == p) continue;
if(sub[u]*2 > sub[node]){
found = 1;
p = cen;
cen = u;
break;
}
}
if(!found){
break;
}
}
// cout << "foundCen: " << cen << "\n";
// cout.flush();
setInSubtree(cen, 1);
genPar(cen);
//solve
vi comps;
queue<int> q;
comps.pb(C[cen]);
comp_inc[C[cen]] = 1;
q.push(C[cen]);
bool bad = 0;
while(sz(q)){
int c = q.front();
q.pop();
for(auto u: invC[c]){
if(!in_subtree[u]){
bad = 1;
break;
}
}
if(bad) break;
for(auto u: invC[c]){
int p = par[u];
if(p == -1) continue;
if(comp_inc[C[p]]) continue;
comps.pb(C[p]);
comp_inc[C[p]] = 1;
q.push(C[p]);
}
}
// cout << "comps: ";
// for(auto u: comps){
// cout << u << " ";
// }
// cout << "\n";
if(!bad){
ckmin(ans, sz(comps)-1);
}
setInSubtree(cen, 0);
for(auto u: comps){
comp_inc[u] = 0;
}
done[cen] = 1;
for(auto u: adj[cen]){
if(done[u]) continue;
centroidDecomp(u);
}
}
int main(){
int N, K;
cin >> N >> K;
for(int i = 1; i <= N-1; i++){
int a, b;
cin >> a >> b;
adj[a].pb(b);
adj[b].pb(a);
}
for(int i = 1; i <= N; i++){
cin >> C[i];
invC[C[i]].pb(i);
}
centroidDecomp(1);
cout << ans << "\n";
}
