https://pintia.cn/problem-sets/1556843855285559296/exam/problems/type/7?problemSetProblemId=1556843936151740420&page=0

#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef pair<ll, ll> PII;
typedef vector<long long> VI;
//#define int long long
#define INF 0x3f3f3f3f
#define endl '\n'
#define N 2020
const int mod = 1e9 + 7;


int n, t[N];
vector<int> g[N];
int vis[N], e[N][N];

void bfs(int x) {
    queue<int> q;
    vis[x] = 1;
    q.push(x);

    while (q.size()) {
        auto t = q.front();
        q.pop();

        for (auto to : g[t]) {
            if (vis[to])continue;

            vis[to] = 1;
            e[x][to] = e[x][t] + 1;
            q.push(to);
        }
    }

}
void solve() {

    cin >> n;

    for (int i = 1; i < n; 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 >> t[i];

    for (int i = 1; i <= n; i++) {
        for (int j = 1; j <= n; j ++)vis[j] = 0;

        bfs(i);
    }

    int res = 0;
    for (int i = 1; i <= n; i ++) {
        for (int j = i + 1; j <= n; j ++) {
            for (int k = j + 1; k <= n; k++) {
                if (e[i][j] == e[j][k] && e[i][j] == e[i][k]) {
                    if (t[i] != t[j] && t[i] != t[k] && t[j] != t[k]) {
                        res ++;
                    }
                }
            }
        }
    }

    cout << res << endl;
}

signed main() {

    ios::sync_with_stdio(false);
    cin.tie(0), cout.tie(0);

    int T = 1;
//  cin >> T;
    while (T --)

        solve();

    return 0;
}