#include <bits/stdc++.h>
#include "race.h"
using namespace std;
const int maxn=2e5+2;
vector<pair<int,int>>ad[maxn];
map<int,int>mp[maxn];
int rs=1e9;
void dfs(int u,int p,int k,int d,int h) {
mp[u][d]=h;
for(auto[v,c]:ad[u]) {
if(v==p)continue;
dfs(v,u,k,d+c,h+1);
if(mp[v].size()>mp[u].size())swap(mp[u],mp[v]);
for(auto[cost,node]:mp[v]){
int rem=k+2*d-cost;
if (mp[u].count(rem)){
rs=min(rs,mp[u][rem]+node-2*h);
}
}
for(auto[cost,node]:mp[v]){
if(!mp[u].count(cost))mp[u][cost]=node;
mp[u][cost]=min(mp[u][cost],node);
}
}
}
int best_path(int n,int k,int h[][2],int l[]){
for(int i=0;i<n-1;i++){
ad[h[i][0]].push_back({h[i][1],l[i]});
ad[h[i][1]].push_back({h[i][0],l[i]});
}
dfs(0,-1,k,0,0);
return rs==(int)1e9?-1:rs;
}
