#include<iostream>
#include<tr1/unordered_map>
#include<utility>
#include<vector>
#include "race.h"
using namespace std;
int N,ui,vi,wi;
long long K;
int big[200005],out=1<<30;
vector <pair<int,int> > adj[200005];
tr1::unordered_map<long long,int> M[200005];
int dfs(int u, int prev, long long depth, int e) {
big[u]=u;
M[u][depth]=e;
for (auto v: adj[u]) {
if (v.first == prev) {continue;}
int res=dfs(v.first,u,depth+v.second,e+1);
if (M[big[u]].size()<M[res].size()) {
swap(big[u],res);
}
for (auto val: M[res]) {
if (M[big[u]].find(K+2*depth-val.first) != M[big[u]].end()) {
out=min(out,M[big[u]][K+2*depth-val.first]+val.second-2*e);
}
}
for (auto val: M[res]) {
if (M[big[u]].find(val.first)==M[big[u]].end()) {
M[big[u]][val.first]=val.second;
} if (M[big[u]][val.first]>val.second) {
M[big[u]][val.first]=val.second;
}
}
}
return(big[u]);
}
int best_path(int n, int k, int H[][2], int L[]) {
K=k;
for (int i=0; i<n-1; i++) {
adj[H[i][0]].push_back({H[i][1],L[i]});
adj[H[i][1]].push_back({H[i][0],L[i]});
} //1 indexify
dfs(0,-1,0,0);
return(out<=n ? out : -1);
}
