#include <iostream>
#include <vector>
#include <cmath>
#include <algorithm>
#include <string>
#include <bitset>
#include <iterator>
#include <iomanip>
#include <map>
#include <set>
#include <unordered_map>
#include <unordered_set>
#include <ctime>
#include <deque>
#include <queue>
#include <stack>
#include <random>
#include <cassert>

using namespace std;

#define int long long
#define all(a) a.begin(), a.end()
#define rall(a) a.rbegin(), a.rend()

typedef long long ll;
typedef long double ld;

mt19937_64 rnd(1329);

void solve() {
    int n, k;
    cin >> n >> k;
    if (n == 1 || k == 1) {
        cout << "0\n";
        return;
    }
    vector<vector<int>> gr(n);
    for (int i = 0; i < n - 1; ++i) {
        int a, b;
        cin >> a >> b;
        --a; --b;
        gr[a].push_back(b);
        gr[b].push_back(a);
    }
    vector<int> ord;
    for (int i = 0; i < n; ++i) {
        if (gr[i].size() != 1) continue;
        ord.push_back(i);
        ord.push_back(gr[i][0]);
        for (int i = 0; i < n - 2; ++i) {
            for (auto e : gr[ord.back()]) {
                if (ord[ord.size() - 2] == e) continue;
                ord.push_back(e);
                break;
            }
        }
        break;
    }
    vector<int> backord(n);
    for (int i = 0; i < n; ++i) {
        backord[ord[i]] = i;
    }
    vector<int> c(n);
    for (int i = 0; i < n; ++i) {
        cin >> c[backord[i]];
    }
    for (int i = 0; i < n; ++i) {
        c[i]--;
    }
    vector<int> L(k, 1e9), R(k, -1);
    for (int i = 0; i < n; ++i) {
        L[c[i]] = min(L[c[i]], i);
        R[c[i]] = max(R[c[i]], i);
    }
    for (int i = 0; i < k; ++i) {
        if (L[i] == R[i]) {
            cout << "0\n";
            return;
        }
    }
    vector<vector<int>> lolkek(k);
    for (int i = 0; i < n; ++i) {
        lolkek[c[i]].push_back(i);
    }
    vector<unsigned long long> LOL(k);
    for (int i = 0; i < k; ++i) {
        LOL[i] = rnd();
    }
    vector<unsigned long long> x(n);
    vector<bool> ok(n);
    for (int i = 0; i < k; ++i) {
        ok[L[i]] = 1;
        x[L[i]] = LOL[i];
        x[R[i]] = LOL[i];
    }
    vector<unsigned long long> px(n + 1);
    for (int i = 0; i < n; ++i) px[i + 1] = (px[i] ^ x[i]);
    vector<int> p2(n + 1);
    for (int i = 0; i < k; ++i) p2[L[i] + 1]++;
    for (int i  = 1; i <= n; ++i) p2[i] += p2[i - 1];
    map<unsigned long long, vector<int>> kek;
    for (int i = 0; i <= n; ++i) {
        kek[px[i]].push_back(i);
    }
    for (auto &e : kek) {
        e.second.push_back(n + 2);
        reverse(e.second.begin(), e.second.end());
    }
    int ans = k - 1;
    set<int> fucked;
    fucked.insert(n + 1);
    for (int i = 0; i < n; ++i) {
        kek[px[i]].pop_back();
        if (!ok[i]) continue;
        int R = kek[px[i]].back();
        while (*fucked.begin() <= i) fucked.erase(fucked.begin());
        int T = *fucked.begin();
        if (T > R) {
            ans = min(ans, p2[R] - p2[i] - 1);
        }
        for (auto e : lolkek[c[i]]) {
            fucked.insert(e);
        }
    }
    cout << ans << '\n';
}

signed main() {
    int tc = 1;
#ifdef LOCAL
    freopen("in.txt", "r", stdin);
    freopen("out.txt", "w", stdout);
#else
    ios_base::sync_with_stdio(0);
    cin.tie(0); cout.tie(0);
#endif
    // cin >> tc;
    for (int t = 1; t <= tc; t++) {
        // cout << "Case #" << t  << ": ";
        solve();
    }
}