/*
IN THE NAME OF GOD
*/
#include <bits/stdc++.h>
// #pragma GCC target("avx2,bmi,bmi2,lzcnt,popcnt")
// #pragma GCC optimize("O3")
// #pragma GCC optimize("unroll-loops")
using namespace std;
typedef long long ll;
typedef pair<ll, ll> pll;
typedef pair<int, int> pii;
typedef long double ld;
#define F first
#define S second
#define Mp make_pair
#define pb push_back
#define pf push_front
#define size(x) ((ll)x.size())
#define all(x) (x).begin(),(x).end()
#define kill(x) cout << x << '\n', exit(0);
#define fuck(x) cout << "(" << #x << " , " << x << ")" << endl
#define endl '\n'
const int N = 2e5+23, lg = 18;
ll Mod = 1e9+7; //998244353;
inline ll MOD(ll a, ll mod=Mod) {a%=mod; (a<0)&&(a+=mod); return a;}
inline ll poww(ll a, ll b, ll mod=Mod) {
ll ans = 1;
a=MOD(a, mod);
while (b) {
if (b & 1) ans = MOD(ans*a, mod);
b >>= 1;
a = MOD(a*a, mod);
}
return ans;
}
int n, k, ans, glob, par[N], cnt[N], vis[N], c[N], sz[N], mark[N];
vector<int> adj[N], g[N];
void init(int v, int p=0, int f=0) {
if(f==1) cnt[c[v]] ++;
sz[v] = 1;
par[v] = p;
for(int u : adj[v]) {
if(u == p || mark[u] == 1) continue;
init(u, v, f);
sz[v] += sz[u];
}
}
int findC(int v, int p=0) {
int res=-1, yey=(glob-sz[v] <= glob/2 ? 1 : 0);
for(int u : adj[v]) {
if(u == p || mark[u] == 1) continue;
res = max(res, findC(u, v));
yey &= (sz[u] <= glob/2);
}
if(yey==1) res = v;
return res;
}
void clen(int v, int p=0) {
cnt[c[v]] = 0, par[v] = 0, sz[v] = 0;
vis[c[v]] = 0;
for(int u : adj[v]) {
if(u == p || mark[u] == 1) continue;
clen(u, v);
}
}
void calc(int v) {
init(v);
glob = sz[v];
v = findC(v);
init(v, 0, 1);
int res = 0;
queue<int> q;
q.push(c[v]);
vis[c[v]] = 1;
while(size(q) > 0) {
int col = q.front();
q.pop();
if(cnt[col] < size(g[col])) {
res = k-1;
break;
}
for(auto u : g[col]) {
if(par[u]!=0 && vis[c[par[u]]]==0) {
vis[c[par[u]]] = 1;
q.push(c[par[u]]);
res++;
}
}
}
clen(v);
mark[v]=1;
ans = min(ans, res);
for(int u : adj[v]) {
if(mark[u] == 0) {
calc(u);
}
}
}
int main () {
ios_base::sync_with_stdio(false), cin.tie(0);
cin>>n>>k; ans = k-1;
for(int v,u,i=1; i<n; i++) {
cin>>v>>u;
adj[v].pb(u);
adj[u].pb(v);
}
for(int i=1; i<=n; i++) {
cin>>c[i];
g[c[i]].pb(i);
}
calc(1);
cout<<ans<<endl;
return 0;
}
