// Judges with GCC >= 12 only needs Ofast
// #pragma GCC optimize("O3,no-stack-protector,fast-math,unroll-loops,tree-vectorize")
// MLE optimization
// #pragma GCC optimize("conserve-stack")
// Old judges
// #pragma GCC target("sse4.2,popcnt,lzcnt,abm,mmx,fma,bmi,bmi2")
// New judges. Test with assert(__builtin_cpu_supports("avx2"));
// #pragma GCC target("avx2,popcnt,lzcnt,abm,bmi,bmi2,fma,tune=native")
// Atcoder
// #pragma GCC target("avx2,popcnt,lzcnt,abm,bmi,bmi2,fma")
/*
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace __gnu_pbds;
typedef tree<int,null_type,less<int>,rb_tree_tag,tree_order_statistics_node_update> ordered_set;
- insert(x),erase(x)
- find_by_order(k): return iterator to the k-th smallest element
- order_of_key(x): the number of elements that are strictly smaller
*/
#include<bits/stdc++.h>
using namespace std;
mt19937_64 rng(chrono::steady_clock::now().time_since_epoch().count());
uniform_real_distribution<> pp(0.0,1.0);
//#define int long long
#define ld long double
#define pii pair<int,int>
#define piii pair<pii,int>
#define mpp make_pair
#define fi first
#define se second
//const int inf=1e18;
const int mod=1e9+7;
const int maxn=200005;
const int bl=650;
const int maxs=655;
const int maxm=200005;
const int maxq=500005;
const int maxl=18;
const int maxa=250000;
const int root=3;
/*
int power(int a,int n){
int res=1;
while(n){
if(n&1) res=res*a%mod;
a=a*a%mod;n>>=1;
}
return res;
}
const int iroot=power(3,mod-2);
*/
const int base=101;
void solve(){
int cnt,n,k;cin >> n >> k;cnt=n*maxl;
vector<vector<int>> par(n+1,vector<int>(maxl,0)),edge(cnt+1),adj(n+1);
vector<int> dep(n+1,0);
for(int i=1;i<n;i++){
int u,v;cin >> u >> v;
adj[u].push_back(v);
adj[v].push_back(u);
}
function<void(int,int)> dfs = [&](int u,int p){
par[u][0]=p;dep[u]=dep[p]+1;
for(int v:adj[u]){
if(v==p) continue;
dfs(v,u);
}
};
dfs(1,0);
vector<int> col(n+1);
for(int i=1;i<=n;i++) cin >> col[i];
for(int i=1;i<maxl;i++){
for(int j=1;j<=n;j++){
par[j][i]=par[par[j][i-1]][i-1];
edge[n*i+j].push_back(n*(i-1)+(i==1?col[j]:j));
if(par[j][i-1]) edge[n*i+j].push_back(n*(i-1)+(i==1?col[par[j][i-1]]:par[j][i-1]));
}
}
auto lca = [=](int u,int v){
if(dep[u]>dep[v]) swap(u,v);
for(int i=0;i<maxl;i++){
if((dep[v]-dep[u])&(1<<i)) v=par[v][i];
}
if(v==u) return u;
for(int i=maxl-1;i>=0;i--){
if(par[u][i]!=par[v][i]){
u=par[u][i];
v=par[v][i];
}
}
return par[u][0];
};
vector<int> pre(k+1,0);
for(int j=1;j<=n;j++){
if(pre[col[j]]){
int u=pre[col[j]],v=j;
int a=par[lca(u,v)][0],cc=col[v];
//cout << u << ' ' << v << '\n';
for(int i=maxl-1;i>=0;i--){
if((dep[u]-dep[a])&(1<<i)){
edge[cc].push_back(i*n+(i==0?col[u]:u));
//cout << cc << ' ' << i*n+(i==0?col[u]) << '\n';
u=par[u][i];
}
}
for(int i=maxl-1;i>=0;i--){
if((dep[v]-dep[a])&(1<<i)){
edge[cc].push_back(i*n+(i==0?col[v]:v));
//cout << cc << ' ' << i*n+(i==0?col[v]:v) << '\n';
v=par[v][i];
}
}
}
pre[col[j]]=j;
}
int pos=0,scc_cnt=0;
vector<int> low(cnt+1,0),num(cnt+1,0),st,scc(cnt+1,-1),val;
vector<bool> inst(cnt+1,false);
int Min=k;
function<void(int)> dfs2 = [&](int u){
num[u]=low[u]=++pos;
st.push_back(u);inst[u]=true;
for(int v:edge[u]){
if(!num[v]){
dfs2(v);
low[u]=min(low[u],low[v]);
}
else if(inst[v]) low[u]=min(low[u],num[v]);
}
if(low[u]==num[u]){
int v=0;val.push_back(0);
do{
v=st.back();st.pop_back();
inst[v]=false;scc[v]=scc_cnt;val.back()+=(v<=k);
//if(v<=k) cout << scc_cnt << ' ' << v << '\n';
}
while(v!=u);
scc_cnt++;
}
};
for(int i=1;i<=cnt;i++){
if(!num[i]) dfs2(i);
}
for(int i=1;i<=cnt;i++){
for(int v:edge[i]){
//cout << i << ' ' << v << ' ' << scc[i] << ' ' << scc[v] << '\n';
if(scc[i]!=scc[v]) val[scc[i]]=k;
}
}
for(int i=0;i<scc_cnt;i++){
if(val[i]) Min=min(Min,val[i]-1);
}
cout << Min << '\n';
}
signed main(){
ios_base::sync_with_stdio(false);
cin.tie(NULL);cout.tie(NULL);
int test=1;//cin >> test;
while(test--) solve();
}
