#include "race.h"
#include <vector>
#include <algorithm>
#include <unordered_map>
using namespace std;
const int MAXN = 200005;
struct EDGE { int x, w; };
int N, K, ans = -1;
vector <EDGE> v[MAXN];
void f(int x, int par, unordered_map <int, int> &d) {
d[0] = 0;
for (auto &y : v[x]) {
if (y.x == par) continue;
unordered_map <int, int> d2, d3;
f(y.x, x, d2);
for (auto &t : d2) {
if (t.first + y.w > K) continue;
d3[t.first + y.w] = t.second + 1;
}
d2.clear();
if (d.size() < d3.size()) d.swap(d3);
for (auto &t : d3) {
if (d.count(K - t.first)) {
if (ans == -1 || ans > d[K - t.first] + t.second)
ans = d[K - t.first] + t.second;
}
}
for (auto &t : d3) {
if (t.first == K) {
if (ans == -1 || ans > t.second)
ans = t.second;
}
if (d.count(t.first)) d[t.first] = min(d[t.first], t.second);
else d[t.first] = t.second;
}
}
}
int best_path(int _N, int _K, int H[][2], int L[]) {
N = _N, K = _K;
for (int i = 0; i < N - 1; i++) {
v[H[i][0]].push_back({ H[i][1], L[i] });
v[H[i][1]].push_back({ H[i][0], L[i] });
}
unordered_map <int, int> d;
f(0, -1, d);
return ans;
}
