#include <bits/stdc++.h>
#include "race.h"
using namespace std;
const int maxn = 1e6 + 5;
const int inf = 1e9 + 7;
int depth[maxn];
int road[maxn];
int n, k;
vector<pair<int, int>> tr[maxn];
void dfs(int u, int p){
for(auto node : tr[u]){
int v = node.first;
int w = node.second;
if(v == p) continue;
depth[v] = depth[u] + 1;
road[v] = road[u] + w;
dfs(v, u);
}
}
int best_path(int N, int K, int H[][2], int L[]){
n = N;
k = K;
for(int i = 0; i < n - 1; i++){
int a, b, l;
a = H[i][0];
b = H[i][1];
l = L[i];
tr[a].push_back({b, l});
tr[b].push_back({a, l});
}
int result = inf;
for(int i = 0; i < n; i++){
depth[i] = 0;
road[i] = 0;
dfs(i, -1);
for(int j = 0; j < n; j++){
if(road[j] == k && result > depth[j]){
result = depth[j];
}
}
}
if(result == inf){
return -1;
}else{
return result;
}
}
