#include "race.h"
#include <bits/stdc++.h>
using namespace std;
#define ff first
#define ss second
int n, k, mn;
vector< pair<int, int> > g[200005];
void dfs(int v, int par, map<int, int> &mp, int depth, long long distance){
mp[distance] = depth;
for(auto [to, w] : g[v]){
if(to == par) continue;
map<int, int> sub;
dfs(to, v, sub, depth + 1, distance + w);
if(mp.size() < sub.size()) swap(mp, sub);
for(auto &u : sub){
int d = 2*distance - u.ff + k;
if(mp.count(d)){
mn = min(mn, mp[d] + u.ss - 2*depth);
}
}
for(auto &u : sub){
if(mp.count(u.ff)) mp[u.ff] = min(mp[u.ff], u.ss);
else{
mp[u.ff] = u.ss;
}
}
}
}
int best_path(int N, int K, int H[][2], int L[]){
n = N, k = K, mn = N+1;
for(int i = 0;i < n-1; i++){
g[H[i][0]].push_back({H[i][1], L[i]});
g[H[i][1]].push_back({H[i][0], L[i]});
}
map<int, int> mp;
dfs(0, 0, mp, 0, 0);
if(mn == n+1) mn = -1;
return mn;
}
//main(){
// int N, K; cin >> N >> K;
// int H[N-1][2], L[N-1];
// for(int i = 0; i < N-1; i++){
// cin >> H[i][0] >> H[i][1];
// }
// for(int i = 0;i < N-1; i++) cin >> L[i];
// cout << best_path(N, K, H, L);
//}
