#include <bits/stdc++.h>
using namespace std;
#ifdef LOCAL
#include "debug.h"
#else
#define debug(...) 42
#endif
const int N = 2e5 + 5, LG = 18, MAX = 3600005;
int n, k, m;
int lst[N], c[N], dep[N], pr[LG][N], id[LG][N], low[MAX], num[MAX], cnt[MAX], lab[MAX];
vector<int> tree[N], g[MAX];
void dfs(int u) {
for (int v : tree[u]) {
if (v != pr[0][u]) {
pr[0][v] = u;
id[0][v] = c[u];
for (int i = 1; i < LG; ++i) {
id[i][v] = ++m;
pr[i][v] = pr[i - 1][pr[i - 1][v]];
g[m].push_back(id[i - 1][v]);
g[m].push_back(id[i - 1][pr[i - 1][v]]);
}
dep[v] = dep[u] + 1;
dfs(v);
}
}
}
int lca(int u, int v) {
if (dep[u] < dep[v]) {
swap(u, v);
}
for (int j = LG - 1; ~j; --j) {
if (dep[u] - (1 << j) >= dep[v]) {
u = pr[j][u];
}
}
if (u == v) {
return u;
}
for (int j = LG - 1; ~j; --j) {
if (pr[j][u] != pr[j][v]) {
u = pr[j][u], v = pr[j][v];
}
}
return pr[0][u];
}
void add(int u, int p) {
int col = c[u];
for (int i = LG - 1; ~i; --i) {
if (dep[u] - (1 << i) >= dep[p]) {
g[col].push_back(id[i][u]);
u = pr[i][u];
}
}
}
int top, timer, scc;
int st[MAX];
void DFS(int u) {
st[++top] = u;
low[u] = num[u] = ++timer;
for (int v : g[u]) {
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]) {
++scc;
while (1) {
int v = st[top--];
num[v] = MAX;
lab[v] = scc;
if (v == u) {
break;
}
}
}
}
int main() {
ios::sync_with_stdio(false); cin.tie(nullptr);
cin >> n >> k; m = k;
for (int i = 1; i < n; ++i) {
int u, v; cin >> u >> v;
tree[u].push_back(v);
tree[v].push_back(u);
}
for (int i = 1; i <= n; ++i) {
cin >> c[i];
}
dfs(1);
for (int i = 1; i <= n; ++i) {
if (lst[c[i]]) {
int x = lca(i, lst[c[i]]);
add(i, x);
add(lst[c[i]], x);
}
lst[c[i]] = i;
}
for (int i = 1; i <= m; ++i) {
if (!num[i]) {
DFS(i);
}
}
for (int i = 1; i <= k; ++i) {
++cnt[lab[i]];
}
vector<int> ver(m);
iota(ver.begin(), ver.end(), 1);
sort(ver.begin(), ver.end(), [&](int i, int j) {
return lab[i] < lab[j];
});
int res = MAX;
for (int i = 1, j = 0; i <= scc; ++i) {
bool out = 0;
while (j < m && lab[ver[j]] == i) {
for (int k : g[ver[j]]) {
if (lab[k] != i && cnt[lab[k]]) {
out = 1;
}
}
j++;
}
if (out) {
cnt[i] = 1;
} else if (cnt[i]) {
res = min(res, cnt[i] - 1);
}
}
cout << res;
return 0;
}
