#include <bits/stdc++.h>
#include "race.h"
using namespace std;
#define ll int
#define ff first
#define ss second
#define all(x) (x).begin(), (x).end()
#define pb push_back
#define ertunt return
#define vodka void
vector<pair<int,int>>v[1000006];
ll ans;
vodka dfs(int i, int j, int cur, int d, int k){
if(cur == k){
ans = min(ans, d);
ertunt;
}
if(cur > k) ertunt;
for(auto [x,y]: v[i]){
if(x != j){
dfs(x, i, cur + y, d + 1, k);
}
}
}
int best_path(int n, int k, int h[][2], int l[]){
for(ll i = 1; i <= n; i++) v[i].clear();
for(ll i = 0; i < n-1; i++){
v[h[i][0]].pb({h[i][1], l[i]});
v[h[i][1]].pb({h[i][0], l[i]});
}
ans = 1e9;
for(ll i = 1; i <= n; i++) dfs(i, -1, 0, 0, k);
ertunt ans == 1e9 ? -1 : ans;
}
