#include "race.h"
#include <bits/stdc++.h>
using namespace std;
int n,k;
vector<pair<int,int>> al[200005];
pair<int,int> offset[200005];
map<int,int> s[200005];
int ans=1000000;
void dfs(int i,int p){
s[i][0]=0;
for (auto [it,w]:al[i]){
if (it==p) continue;
dfs(it,i);
offset[it].first+=w;
offset[it].second++;
if (s[it].size()>s[i].size()){
swap(s[it],s[i]);
swap(offset[it],offset[i]);
}
for (auto x:s[it]){
int t=k-x.first-offset[i].first-offset[it].first;
if (s[i].count(t)) ans=min(ans,s[i][t]+offset[i].second+x.second+offset[it].second);
}
for (auto x:s[it]){
int t=x.first+offset[it].first-offset[i].first;
if (s[i].count(t)) s[i][t]=min(s[i][t],x.second+offset[it].second-offset[i].second);
else s[i][t]=x.second+offset[it].second-offset[i].second;
}
}
}
int best_path(int N, int K, int h[][2], int l[]){
n=N,k=K;
for (int x=0;x<n-1;x++){
al[h[x][0]].push_back({h[x][1],l[x]});
al[h[x][1]].push_back({h[x][0],l[x]});
}
dfs(0,-1);
return (ans==1000000)?-1:ans;
}
