#include <bits/stdc++.h>
#include "race.h"
using namespace std;
const int mxN = 2e5 + 5;
vector<pair<int, int>> ad[mxN];
map<int, int> mp[mxN];
int ans = 1e9;
void dfs(int u, int p, int k, int d, int h) {
mp[u][d] = h;
for (auto [v, w] : ad[u]) {
if (v == p) continue;
dfs(v, u, k, d + w, h + 1);
if (mp[v].size() > mp[u].size()) {
swap(mp[u], mp[v]);
}
for (auto [i, j] : mp[v]) {
if (k + 2 * d - i >= 0 && mp[u].find(k + 2 * d - i) != mp[u].end()) {
ans = min(ans, mp[u][k + 2 * d - i] + mp[v][i] - 2 * h);
}
}
for (auto [i, j] : mp[v]) {
if (!mp[u][i]) mp[u][i] = j;
else mp[u][i] = min(mp[u][i], j);
}
}
}
int best_path(int N, int K, int H[][2], int L[]) {
for (int i = 0; i < N - 1; i++) {
ad[H[i][0] + 1].push_back({H[i][1] + 1, L[i]});
ad[H[i][1] + 1].push_back({H[i][0] + 1, L[i]});
}
dfs(1, -1, K, 0, 1);
if (ans == 1e9) ans = -1;
return ans;
}
