/*
#pragma GCC optimize("O2")
#pragma GCC optimize("Ofast")
#pragma GCC optimize("unroll-loops")
#pragma GCC target("avx,avx2,sse,sse2,fma")
*/
#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef long double ld;
typedef pair<int , int> pii;
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
const int maxn = 2e5 + 100;
const ll mod = 1e9+7;
const ld PI = acos((ld)-1);
#define pb push_back
#define endl '\n'
#define dokme(x) cout << x , exit(0)
#define migmig ios::sync_with_stdio(false),cin.tie(0),cout.tie(0)
#define ms(x , y) memset(x , y , sizeof x)
ll pw(ll a, ll b, ll md = mod){ll res = 1;while(b){if(b&1){res=(a*res)%md;}a=(a*a)%md;b>>=1;}return(res);}
vector < int > adj[maxn], col[maxn];
int n , k , c[maxn];
int sz[maxn] , hide[maxn] , ans = 1e9;
int par[maxn];
void plant(int v , int p = 0){
sz[v] = 1;
for(int u : adj[v])if(u ^ p and !hide[u])
plant(u , v) , sz[v] += sz[u];
}
int cen(int v , int n , int par = 0 , bool found = 0){
while(!found){
found = 1;
for(int u : adj[v]) if(!hide[u] and u != par and sz[u] * 2 > n){
par = v , v = u , found = 0;
break;
}
}
return(v);
}
struct sett{
vector < int > und;
int cnt[maxn];
void insert(int x){
cnt[x] ++;
if(cnt[x] == 1)und.pb(x);
}
void clear(){
for(int x : und)cnt[x] = 0;
und.clear();
}
int count(int x){
return(cnt[x]);
}
}st;
queue < int > colors;
int mark[maxn];
int comp[maxn] , cmp = 0;
void dfs(int v , int p = 0){
comp[v] = cmp , mark[v] = 0 , par[v] = p;
for(auto u : adj[v])if(!hide[u] and u != p)
par[u] = v , dfs(u , v);
}
int calc(int v){
cmp = v;
dfs(v);
while(colors.size())
colors.pop();
colors.push(c[v]);
st.clear();
st.insert(c[v]);
int ans = 0;
while(!colors.empty()){
ans ++;
int color = colors.front();
colors.pop();
for(auto u : col[color]){
if(comp[u] != v)return(1e9);
if(u != v and !st.count(c[par[u]]))
st.insert(c[par[u]]) , colors.push(c[par[u]]);
}
}
return(ans - 1);
}
void solve(int v){
plant(v);
v = cen(v , sz[v]);
ans = min(ans , calc(v));
hide[v] = 1;
for(int u : adj[v])
if(!hide[u])
solve(u);
}
int32_t main(){
migmig;
cin >> n >> k;
if(k > n/2)dokme(0);
for(int i = 1 ; i < n; i ++){
int u , v;
cin >> u >> v;
adj[u].pb(v);
adj[v].pb(u);
}
for(int i = 1 ; i <= n ; i ++) cin >> c[i] , col[c[i]].pb(i);
solve(1);
cout << ans;
return(0);
}
