#include<bits/stdc++.h>
#include "race.h"
using namespace std;
#define pb push_back
#define F first
#define S second
const int N = 2e5+3;
int inf=1e9;
vector<pair<int, int>> adj[N];
int d[N];
int c[N];
int x;
int ans=inf;
map<int, int> mapa[N];
void dfs(int v, int p, int dep, int cost){
c[v]=cost;
d[v]=dep;
for(auto to : adj[v]){
if(to.F!=p){
dfs(to.F, v, dep+1, cost+to.S);
}
}
}
void bst(int v, int p){
mapa[v][c[v]]=d[v];
for(auto to : adj[v]){
if(to.F!=p){
bst(to.F, v);
if(mapa[to.F].size()>mapa[v].size())mapa[v].swap(mapa[to.F]);
for(auto it : mapa[to.F]){
int wnt=x+2*c[v]-it.F;
if(mapa[v].count(wnt))ans=min(ans, mapa[v][wnt]+it.S-2*d[v]);
}
for(auto it : mapa[to.F]){
if(mapa[v].count(it.F))mapa[v][it.F]=min(mapa[v][it.F], it.S);
else mapa[v][it.F]=it.S;
}
if(mapa[v].count(x+c[v])){
ans=min(ans, mapa[v][x+c[v]]-d[v]);
}
}
}
}
int best_path(int n, int k, int h[][2], int l[])
{
x=k;
for(int i=0; i< n-1; i++){
adj[h[i][0]].pb({h[i][1], l[i]});
adj[h[i][1]].pb({h[i][0], l[i]});
}
dfs(0, -1, 0, 0);
bst(0, -1);
if(ans==inf)return -1;
else return ans;
}
