VOI 2020 COMNET

#include <bits/stdc++.h>

using namespace std;
using ll = long long;
using ld = long double;
using ull = unsigned long long;

constexpr bool typetest = 0;
constexpr int N = 1e3 + 5;

int n, k, a, b, cnt[N];
ll dp[N][N][5], ans(0);
vector<int> adj[N];

void Read()
{
    cin >> n >> k >> a >> b;
    for (int i = 1; i < n; ++i)
    {
        int u, v;
        cin >> u >> v;
        adj[u].emplace_back(v);
        adj[v].emplace_back(u);
    }
}

void dfs(int v, int p)
{
    dp[v][0][0] = dp[v][0][1] = 1;
    cnt[v] = 1;
    for (auto i : adj[v])
        if (i != p)
        {
            dfs(i, v);
            cnt[v] += cnt[i];
            for (int h = k; h; --h)
                for (int l = 1; l <= h; ++l)
                    for (int j = 1; j <= cnt[v]; ++j)
                        for (int t = 0; t < j && t <= cnt[i]; ++t)
                            dp[v][j][h] += dp[v][j - t - 1][h - l] * dp[i][t][l];

            for (int j = a; j <= b; ++j)
                ans -= dp[i][j - 1][k];
        }

    for (int j = a; j <= b; ++j)
        ans += dp[v][j][k];

    /*cout << v << ":\n";
    for (int l = 0; l <= k; ++l)
        for (int j = 0; j <= n; ++j)
            cout << dp[v][j][l] << (j == n ? "\n" : " ");
*/
}

void Solve()
{
    dfs(1, 1);
    cout << ans;
}

int32_t main()
{
    ios::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);
    int t(1);
    if (typetest)
        cin >> t;
    for (int _ = 1; _ <= t; ++_)
    {
        Read();
        Solve();
    }
}