#include <bits/stdc++.h>
#include "race.h"
#define int64 long long
using namespace std;
const int maxn = 2e5 + 2;
vector <pair <int, int> > ad[maxn];
map <int, int> mp [maxn];
int rs = 1e9;
void dfs (int u, int p, int k, int d, int h) {
// cerr << u << " " << p << " " << k << " " << d << " " << h << "\n";
mp[u][d] = h;
for (auto [v, c]: ad[u]) {
if (v == p) continue;
dfs(v, u, k, d + c, h + 1);
if (mp[v].size() > mp[u].size()) swap(mp[u], mp[v]);
for (auto [cost, node]: mp[v]) {
int rem = k + 2 * d - cost;
if (mp[u].count(rem)) {
// cout << u << " " << cost << " " << rem << "\n";
rs = min(rs, mp[u][rem] + node - 2 * h);
}
}
for (auto [cost, node]: mp[v]) {
if (!mp[u].count(cost)) mp[u][cost] = node;
mp[u][cost] = min(mp[u][cost], node);
}
}
// if (mp[u].count(k + d)) rs = min(rs, mp[u][k + d] - h);
}
int best_path(int n, int k, int h[][2], int l[]){
for (int i = 0; i < n - 1; i++){
ad[h[i][0]].push_back({h[i][1], l[i]});
ad[h[i][1]].push_back({h[i][0], l[i]});
}
dfs(0, -1, k, 0, 0);
return rs == (int) 1e9 ? -1 : rs;
}
