#include <bits/stdc++.h>
#include "race.h"
using namespace std;
using ll = long long;
const int MAXN = 2e5 + 10;
ll dist[MAXN];
vector<pair<int, ll>> adj[MAXN];
map<ll, int> freq[MAXN];
int ans, k;
void merge(int u, int v, int d){
if(freq[u].size() > freq[v].size()) swap(freq[u], freq[v]);
for(auto x : freq[u]){
if(freq[v].count(k + 2 * dist[v] - x.first)){
ans = min(ans, x.second + freq[v][k + 2 * dist[v] - x.first] - 2 * d);
}
}
for(auto x : freq[u]){
if(freq[v].count(x.first)){
freq[v][x.first] = min(freq[v][x.first], x.second);
} else freq[v][x.first] = x.second;
}
freq[u].clear();
}
void dfs(int v, int p, int d){
freq[v][dist[v]] = d;
for(auto [u, w] : adj[v]){
if(u != p){
dist[u] = dist[v] + w;
dfs(u, v, d + 1);
merge(u, v, d);
}
}
}
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] + 1].push_back({h[i][1] + 1, l[i]});
adj[h[i][1] + 1].push_back({h[i][0] + 1, l[i]});
}
ans = 1e9;
dfs(1, 1, 0);
return (ans == 1e9 ? -1 : ans);
}
