#include <bits/stdc++.h>
using namespace std;
#define foru(i,a,b) for(int i=(a); i<=(b); ++i)
#define ford(i,a,b) for(int i=(a); i>=(b); --i)
#define rep(i,a) for(int i=0; i<(a); ++i)
#define bit(s,i) (((s)>>(i))&1)
#define all(a) (a).begin(),(a).end()
#define sz(a) (int)(a).size()
#define ii pair<int,int>
#define fi first
#define se second
#define eb emplace_back
#define pb push_back
#define ll long long
#define __builtin_popcount(a) __builtin_popcountll(a)
template <class X, class Y> bool maxi(X &x, Y y){return x<y?x=y,true:false;}
template <class X, class Y> bool mini(X &x, Y y){return x>y?x=y,true:false;}
const int N=2e5+5;;
const int N2=1e6+5;
int n,k,c[N];
vector<int> adj[N],lst[N];
void input(){
cin>>n>>k;
rep(i,n-1){
int u,v; cin>>u>>v;
adj[u].eb(v); adj[v].eb(u);
}
foru(i,1,n) cin>>c[i], lst[c[i]].eb(i);
}
int sz[N],up[N][20],h[N];
void pre(int u, int p=-1){
sz[u]=1;
for(int v:adj[u]) if(v!=p){
up[v][0]=u;
foru(i,1,17) up[v][i]=up[up[v][i-1]][i-1];
h[v]=h[u]+1;
pre(v,u);
sz[u]+=sz[v];
}
}
int lca(int u, int v){
if(h[u]<h[v]) swap(u,v);
int d=h[u]-h[v];
foru(i,0,17) if(bit(d,i)) u=up[u][i];
if(u==v) return u;
ford(i,17,0) if(up[u][i]!=up[v][i]) u=up[u][i], v=up[v][i];
return up[u][0];
}
int head[N],idCh[N],curCh;
int tin[N],tout[N],tour[N],tim;
void hld(int u, int p=-1){
if(!head[curCh]){
head[curCh]=u;
}
idCh[u]=curCh;
tin[u]=++tim;
tour[tim]=u;
int bigC=-1;
for(int v:adj[u]) if(v!=p){
if(bigC==-1 || sz[bigC]<sz[v]) bigC=v;
}
if(bigC!=-1) hld(bigC,u);
for(int v:adj[u]) if(v!=p && v!=bigC){
++curCh;
hld(v,u);
}
tout[u]=tim;
}
vector<int> nw[N2];
int st[N2],cur;
void build(int id, int l, int r){
st[id]=++cur;
foru(i,l,r){
nw[st[id]].eb(c[tour[i]]);
}
if(l==r) return;
int mid=(l+r)>>1;
build(id<<1,l,mid);
build(id<<1|1,mid+1,r);
}
void buildTree(){
cur=k;
build(1,1,n);
}
void updTree(int u, int v, int val, int id=1, int l=1, int r=n){
if(u>r||v<l) return;
if(u<=l && r<=v){
nw[val].eb(st[id]);
return;
}
int mid=(l+r)>>1;
updTree(u,v,val,id<<1,l,mid);
updTree(u,v,val,id<<1|1,mid+1,r);
}
void add(int x, int y, int p){
while(idCh[x]!=idCh[y]){
updTree(tin[head[idCh[x]]],tin[x],p);
x=up[head[idCh[x]]][0];
}
updTree(tin[y],tin[x],p);
}
void upd(int x, int y, int p){
int l=lca(x,y);
add(x,l,p);
add(y,l,p);
}
void buildEdge(){
foru(i,1,k){
sort(all(lst[i]), [](int x, int y){return tin[x]<tin[y];});
foru(j,0,sz(lst[i])-2){
upd(lst[i][j], lst[i][j+1], i);
}
}
}
int low[N2],num[N2],idcc[N2],numcc,szK[N2];
int stk[N2],top; bool del[N2];
void dfs(int u){
low[u]=num[u]=++tim;
stk[++top]=u;
for(int v:nw[u]){
if(del[v]) continue;
if(!num[v]){
dfs(v);
low[u]=min(low[u],low[v]);
} else{
low[u]=min(low[u],num[v]);
}
}
if(low[u]==num[u]){
++numcc;
int v;
do {
v=stk[top]; --top;
del[v]=true;
idcc[v]=numcc;
if(v<=k) ++szK[numcc];
}
while(v!=u);
}
}
int out[N2];
void compressGraph(){
tim=0;
foru(i,1,cur) if(!num[i]) dfs(i);
foru(u,1,cur){
for(int v:nw[u]){
if(idcc[u]!=idcc[v]){
out[idcc[u]]++;
}
}
}
}
void answer(){
int res=1e9;
foru(i,1,numcc){
if(!out[i]) mini(res,szK[i]);
}
cout<<res-1<<'\n';
}
void solve(){
input();
pre(1); hld(1);
buildTree();
buildEdge();
compressGraph();
answer();
}
int32_t main(){
#define task "test"
if(fopen(task".inp","r")){
freopen(task".inp","r",stdin);
freopen(task".out","w",stdout);
}
cin.tie(0)->sync_with_stdio(0);
solve();
}
