#include <bits/stdc++.h>
using namespace std;
template<typename T>
void out(T x) { cout << x << endl; exit(0); }
#define watch(x) cout << (#x) << " is " << (x) << endl
using ll = long long;
const int maxn = 1e6 + 5;
int n, k;
vector<int> g[maxn];
int c[maxn];
vector<int> C[maxn];
int ans = 1e9;
bool viz[maxn];
int siz[maxn];
void dfs1(int at, int p) {
siz[at]=1;
for (int to: g[at]) {
if (viz[to]) continue;
if (to==p) continue;
dfs1(to,at);
siz[at]+=siz[to];
}
}
int findCenter(int at) {
dfs1(at,-1);
int S = siz[at];
while (true) {
int nxt = -1;
for (int to: g[at]) {
if (viz[to]) continue;
if (siz[to]>siz[at]) continue;
if (siz[to]*2 >= S) {
nxt = to;
break;
}
}
if (nxt==-1) break;
at=nxt;
}
return at;
}
int par[maxn];
int center[maxn];
void dfs2(int at, int p, int cent) {
par[at] = p;
center[at] = cent;
for (int to: g[at]) {
if (viz[to]) continue;
if (to==p) continue;
dfs2(to,at,cent);
}
}
bool vizcol[maxn];
void solve(int at) {
int At = findCenter(at);
dfs2(At,At,At);
bool ok = true;
queue<int> qq;
vector<int> res;
int cnt = -1;
qq.push(At);
while (ok && !qq.empty()) {
int at = qq.front();
++cnt;
qq.pop();
while (ok) {
if (center[at]==0) break;
if (!vizcol[c[at]]) {
cnt -= C[c[at]].size();
vizcol[c[at]] = true;
res.push_back(c[at]);
for (int to: C[c[at]]) {
qq.push(to);
if (center[to]!=At) {
ok = false;
break;
}
}
}
center[at]=0;
at = par[at];
if (at==At) break;
}
}
for (int cc: res) {
vizcol[cc] = false;
}
if (cnt==0) {
ans = min(ans, (int)res.size());
}
viz[At] = true;
for (int to: g[At]) {
if (!viz[to]) {
solve(to);
}
}
}
int main() {
ios_base::sync_with_stdio(false); cin.tie(0); cout.tie(0);
cin>>n>>k;
for (int i=0; i<n-1; i++) {
int u,v; cin>>u>>v;
g[u].push_back(v);
g[v].push_back(u);
}
for (int i=1; i<=n; i++) {
cin>>c[i];
C[c[i]].push_back(i);
}
solve(1);
cout<<ans-1<<endl;
return 0;
}
