#pragma GCC optimize("Ofast")
#include "race.h"
#include<bits//stdc++.h>
using namespace std;
const int n=2e5;
using ll = long long;
int k,ans=n+5;
vector<vector<pair<int,int>>>graph;
map<int,int>dp[n];
ll sum[n+1],ds[n+1];
void dfs(int u,int p){
dp[u][sum[u]]=ds[u];
int v,l;
for(auto&i:graph[u])if(i.first!=p){
ds[i.first]=ds[u]+1;
sum[i.first]=sum[u]+i.second;
dfs(v=i.first,u);
if(dp[u].size()<dp[v].size())swap(dp[u],dp[v]);
for(auto&j:dp[v]){
if(dp[u].find(k+sum[u]-j.first)!=end(dp[u]))
ans=min(ans*1ll,dp[u][k+sum[u]-j.first]+j.second-2*ds[u]);
}
for(auto&j:dp[v]){
if(dp[u].find(j.first)==end(dp[u]))dp[u][j.first]=j.second;
else dp[u][j.first]=min(dp[u][j.first],j.second);
}
dp[v].clear();
}
}
int best_path(int N, int K, int H[][2], int L[])
{
graph.resize(N);
for(int i=0;i<N-1;++i){
graph[H[i][0]].push_back({H[i][1],L[i]});
graph[H[i][1]].push_back({H[i][0],L[i]});
}
k=K;
dfs(0,0);
return (ans==n+5?-1:ans);
}
