Code
#include <bits/stdc++.h>
using namespace std;
const int MAX = 2e5+50;

int n, k1, k2;
int64_t ans;
vector<int> gr[MAX];
int dad[MAX], sub[MAX];
bool rem[MAX];

int b[MAX];

void init(int sz) {
    for (int idx = 1; idx <= sz+1; ++idx)
        b[idx] = 0;
}

void add(int idx, int val, int sz) {
    for (++idx; idx <= sz+1; idx += (idx & -idx)) {
        b[idx] += val;
    }
}

int64_t sum(int idx, int sz) {
    if (idx < 0) return 0;
    idx = min(idx, sz);
    int64_t res = 0;
    for (++idx; idx > 0; idx -= (idx & -idx)) {
        res += b[idx];
    }
    return res;
}

int64_t query(int l, int r, int sz) {
    return sum(r, sz)-sum(l-1, sz);
}

int dfs(int u, int par) {
    sub[u] = 1;
    for (int to : gr[u]) if (to != par and !rem[to]) {
        sub[u] += dfs(to, u);
    }
    return sub[u];
}

int centroid(int u, int par, int sz) {
    for (int to : gr[u])
        if (to != par and !rem[to] and sub[to] > sz/2)
            return centroid(to, u, sz);
    return u;
}

void getChildren(int u, int par, int d, vector<int> &v) {
    v.push_back(d);
    for (int to : gr[u]) {
        if (!rem[to] and to != par) {
            getChildren(to, u, d+1, v);
        }
    }
}

int decomp(int u, int par) {
    int sz = dfs(u, par);
    int c = centroid(u, par, sz);
    if (par == -1)
        par = c;
    rem[c] = true;
    dad[c] = par;

    init(sz);
    add(0, 1, sz);
    for (int to : gr[c]) if (!rem[to]) {
        vector<int> v;
        getChildren(to, c, 1, v);
        for (int x : v) {
            ans += query(k1-x, k2-x, sz);
        }
        for (int x : v) {
            add(x, 1, sz);
        }
    }

    for (int to : gr[c]) if (!rem[to])
        decomp(to, c);
    return c;
}

int main() {
    cin.tie(0)->sync_with_stdio(0);
    cin >> n >> k1 >> k2;
    for (int i = 0, a, b; i < n-1; ++i) {
        cin >> a >> b, --a, --b;
        gr[a].push_back(b);
        gr[b].push_back(a);
    }
    decomp(0, -1);
    cout << ans << '\n';
}