//#pragma GCC optimize("O3")
#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
#define trav(x,a) for (const auto& x: a)
#define sz(x) (int)(x).size()
#define mem(a,v) memset((a), (v), sizeof (a))
#define enl printf("\n")
#define case(t) printf("Case #%d: ", (t))
#define ni(n) scanf("%d", &(n))
#define nl(n) scanf("%I64d", &(n))
#define nai(a, n) for (int _i = 0; _i < (n); _i++) ni(a[_i])
#define nal(a, n) for (int _i = 0; _i < (n); _i++) nl(a[_i])
#define pri(n) printf("%d\n", (n))
#define prl(n) printf("%I64d\n", (n))
#define pii pair<int, int>
#define pll pair<long long, long long>
#define vii vector<pii>
#define vll vector<pll>
#define vi vector<int>
#define vl vector<long long>
#define pb push_back
#define mp make_pair
#define st first
#define nd second
using namespace std;
using namespace __gnu_pbds;
typedef long long ll;
typedef cc_hash_table<int,int,hash<int>> ht;
typedef tree<int,null_type,less<int>,rb_tree_tag,tree_order_statistics_node_update> oset;
const double pi = acos(-1);
const int mod = 1e9 + 7;
const int inf = 1e9 + 7;
const int N = 1e6 + 5;
const double eps = 1e-9;
#define log2(x) (31 - __builtin_clz(x))
struct sparse_table {
int n;
vector<int> a;
vector<vector<int>> st;
int combine(int dl, int dr) {
return a[dl] > a[dr] ? dl : dr;
}
sparse_table() {}
sparse_table(vector<int> & a) : n(a.size()), a(a), st(log2(n) + 1, vector<int>(n)) {
for (int i = 0; i < n; i++)
st[0][i] = i;
for (int j = 1; 1 << j <= n; j++)
for (int i = 0; i + (1 << j) <= n; i++)
st[j][i] = combine(st[j - 1][i], st[j - 1][i + (1 << (j - 1))]);
}
// query the data on the range [l, r[
int query(int l, int r) {
int s = log2(r - l);
return combine(st[s][l], st[s][r - (1 << s)]);
}
};
struct lowest_common_ancestor {
int n, m = 0;
vector<int> a, v, h, par;
vector<vector<int>>& e;
sparse_table st;
lowest_common_ancestor(vector<vector<int>> & e, int r) : n(e.size()), a(n), v(2 * n - 1), h(2 * n - 1), e(e), par(n) {
dfs(r);
st = sparse_table(h);
}
void dfs(int i, int p = -1, int d = 0) {
par[i] = p;
a[i] = m; v[m] = i; h[m++] = d;
for (int j : e[i]) {
if (j == p)
continue;
dfs(j, i, d - 1);
v[m] = i; h[m++] = d;
}
}
// calculate the lowest common ancestor of x and y
int lca(int x, int y) {
return v[st.query(min(a[x], a[y]), max(a[x], a[y]) + 1)];
}
int ok(int x, int y) {
return lca(par[x], y) == y;
}
};
struct strongly_connected_components {
int n, v = 0, c = 0;
vector<bool> ins;
vector<int> s, num, low, com, cnt;
vector<vector<int>>& e;
strongly_connected_components(vector<vector<int>> & e) : n(e.size()), ins(n), num(n, -1), low(n), com(n), e(e), cnt(n) {
for (int i = 0; i < n; i++)
if (num[i] == -1)
dfs(i);
for (int i = 0; i < n; i++)
trav(x, e[i])
if (com[x] != com[i])
cnt[com[i]] = n+1;
}
// use commented lines for biconnected components in undirected graphs
void dfs(int i) {
// void dfs(int i, int p = -1) {
num[i] = low[i] = v++;
s.push_back(i); ins[i] = true;
for (int j : e[i]) {
// if (j == p) {
// p = -1;
// continue;
// }
if (num[j] == -1)
dfs(j);
// dfs(j, i);
if (ins[j])
low[i] = min(low[i], low[j]);
}
if (low[i] == num[i]) {
int j;
do {
j = s.back(); s.pop_back(); ins[j] = false;
com[j] = c;
cnt[c]++;
} while (j != i);
c++;
}
}
};
int en[N], c[N];
// vector<int> st[N], adj[N];
vector<vector<int>> e;
int main() {
int n, k; scanf("%d %d", &n, &k);
e.resize(n);
for (int i = 1, u, v; i < n; i++) {
scanf("%d %d", &u, &v); u--, v--;
e[u].push_back(v);
e[v].push_back(u);
}
for (int i = 0; i < n; i++) {
scanf("%d", &c[i]); c[i]--;
en[c[i]] = i;
}
lowest_common_ancestor l(e, 0);
for (int i = 0; i < n; i++)
en[c[i]] = l.lca(en[c[i]], i);
vector<vector<int>> f(k);
for (int i = 0; i < n; i++) {
if (l.par[i] != -1 && c[i] != c[l.par[i]] && l.ok(i, en[c[i]])) {
f[c[i]].pb(c[l.par[i]]);
// cout << c[i]+1 << " " << c[l.par[i]]+1 << endl;
}
}
strongly_connected_components sc(f);
int ans = k-1;
for (int i = 0; i < sc.c; i++)
ans = min(ans, sc.cnt[i] - 1);
printf("%d\n", ans);
return 0;
}
