#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
#define MASK(i) (1ULL << (i))
#define GETBIT(mask, i) (((mask) >> (i)) & 1)
#define ALL(v) (v).begin(), (v).end()
ll max(ll a, ll b){return (a > b) ? a : b;}
ll min(ll a, ll b){return (a < b) ? a : b;}
ll gcd(ll a, ll b){return __gcd(a, b);}
ll lcm(ll a, ll b){return a / gcd(a, b) * b;}
ll LASTBIT(ll mask){return (mask) & (-mask);}
int pop_cnt(ull mask){return __builtin_popcountll(mask);}
int ctz(ull mask){return __builtin_ctzll(mask);}
int logOf(ull mask){return 63 - __builtin_clzll(mask);}
mt19937_64 rng(chrono::high_resolution_clock::now().time_since_epoch().count());
ll rngesus(ll l, ll r){return l + (ull) rng() % (r - l + 1);}
double rngesus_d(double l, double r){
double cur = rngesus(0, MASK(60) - 1);
cur /= MASK(60) - 1;
return l + cur * (r - l);
}
template <class T1, class T2>
bool maximize(T1 &a, T2 b){
if (a < b) {a = b; return true;}
return false;
}
template <class T1, class T2>
bool minimize(T1 &a, T2 b){
if (a > b) {a = b; return true;}
return false;
}
template <class T>
void printArr(T container, string separator = " ", string finish = "\n", ostream &out = cout){
for(auto item: container) out << item << separator;
out << finish;
}
template <class T>
void remove_dup(vector<T> &a){
sort(ALL(a));
a.resize(unique(ALL(a)) - a.begin());
}
const int N = 2e5 + 69, LOG_N = 18;
int n, k;
vector<int> graph[N];
int a[N], l[N], h[N];
int parent[N][LOG_N];
int dfs_cnt = 0;
void dfs(int u, int p){
l[u] = ++dfs_cnt;
h[u] = h[p] + 1;
for(int j = 1; (int)MASK(j) < h[u]; ++j)
parent[u][j] = parent[parent[u][j-1]][j-1];
for(int v: graph[u]) if (v != p){
parent[v][0] = u;
dfs(v, u);
}
}
int LCA(int u, int v){
if (h[u] < h[v]) swap(u, v);
int diff = h[u] - h[v];
for(int j = 0; j < LOG_N; ++j) if (GETBIT(diff, j))
u = parent[u][j];
if (u == v) return u;
for(int j = LOG_N - 1; j >= 0; --j) if (parent[u][j] != parent[v][j]){
u = parent[u][j];
v = parent[v][j];
}
return parent[u][0];
}
int sum_path(int u, int v){
return h[u] + h[v] - 2 * h[LCA(u, v)];
}
struct DSU{
int n;
vector<int> parent, sz, lck;
vector<vector<int>> S;
DSU(int _n){
n = _n;
parent.resize(n+1); sz.resize(n+1, 1);
lck.resize(n+1); S.resize(n+1);
for(int i = 0; i<=n; ++i) parent[i] = i;
}
int find_set(int u){return (u == parent[u]) ? u : (parent[u] = find_set(parent[u]));}
bool same_set(int u, int v){return find_set(u) == find_set(v);}
bool join_set(int u, int v){
u = find_set(u), v = find_set(v);
if (u != v){
if (sz[u] < sz[v]) swap(u, v);
parent[v] = u;
sz[u] += sz[v];
lck[u] = LCA(lck[u], lck[v]);
for(int i: S[v]) S[u].push_back(i);
return true;
}
return false;
}
int get_size(int u){return sz[find_set(u)];}
int get_lck(int u){return lck[find_set(u)];}
int get_top(int u){
if (S[find_set(u)].empty()) return -1;
int cur = S[find_set(u)].back();
S[find_set(u)].pop_back();
return cur;
}
void push_cc(int u, int v){
S[find_set(u)].push_back(v);
}
};
void go(int i, int &ans, vector<int> &num, vector<int> &low, DSU &mst){
num[i] = low[i] = ++dfs_cnt;
while(true){
int u = mst.get_top(i);
if (u == -1) break;
if (u == mst.get_lck(i)) continue;
int j = a[parent[u][0]];
if (mst.same_set(i, j)) continue;
if (num[j] == 0){
go(a[parent[u][0]], ans, num, low, mst);
}
minimize(low[i], low[j]);
mst.join_set(i, j);
}
mst.push_cc(i, mst.get_lck(i));
if (num[i] == low[i])
minimize(ans, mst.get_size(i) - 1);
}
void solve(){
cin >> n >> k;
for(int i = 1; i<n; ++i){
int u, v; cin >> u >> v;
graph[u].push_back(v);
graph[v].push_back(u);
}
for(int i = 1; i<=n; ++i) cin >> a[i];
dfs(1, 0);
vector<vector<int>> hype(k+1);
for(int i= 1; i<=n; ++i) hype[a[i]].push_back(i);
DSU mst(k);
for(int i = 1; i <= k; ++i){
mst.lck[i] = LCA(hype[i][0], hype[i].back());
for(int j: hype[i])
mst.S[i].push_back(j);
}
vector<int> num(k+1), low(k+1);
int ans = 1e9 + 69;
dfs_cnt = 0;
for(int i= 1; i<=k; ++i) if (num[i] == 0){
go(i, ans, num, low, mst);
}
cout << ans << "\n";
}
int main(void){
ios::sync_with_stdio(0);cin.tie(0); cout.tie(0);
clock_t start = clock();
solve();
cerr << "Time elapsed: " << clock() - start << " ms\n";
return 0;
}
