#include<bits/stdc++.h>
using namespace std;
using ll=long long;
using pii=pair<int,int>;
int best_path(int n, int k, int h[][2], int l[]){
vector<vector<pair<int,int>>>adj(n);
for(int i=0;i<n-1;i++){
int u=h[i][0],v=h[i][1],w=l[i];
adj[u].push_back({v,w});
adj[v].push_back({u,w});
}
vector<int>tin(n),tout(n),hp(n,-1),fls(n);
vector<ll>flw(n);
int tt=0;
auto dfs=[&](auto &&self,int now,int pre,ll ws,int sd)->void{
tin[now]=tt;
fls[tt]=sd;
flw[tt]=ws;
tt++;
int mx=0,hc=-1;
for(auto [nei,w]:adj[now]){
if(nei==pre)continue;
int before=tt;
self(self,nei,now,ws+w,sd+1);
int sub=tt-before;
if(mx<sub){
mx=sub;
hc=nei;
}
}
if(hc!=-1)hp[hc]=now;
tout[now]=tt; //subtree [tin,tout)
};
dfs(dfs,0,-1,0LL,0);
const int INF=1e9;
int ans=INF;
for(int leaf=0;leaf<n;leaf++){
if(tin[leaf]+1!=tout[leaf])continue;
unordered_map<ll,int>dp; //sw, min edge
auto add=[&](int idx){
ll d=flw[idx];
int s=fls[idx];
if(!dp.count(d))dp[d]=s;
else dp[d]=min(dp[d],s);
};
auto relax=[&](int idx,int lca){
ll need=k+2*flw[lca]-flw[idx];
if(dp.count(need)){
ans=min(ans,fls[idx]+dp[need]-2*fls[lca]);
}
};
add(tin[leaf]);
for(int i=leaf;hp[i]!=-1;i=hp[i]){
int p=hp[i];
for(auto[child,_]:adj[p]){
if(fls[tin[child]]>fls[tin[p]] and child!=i){
for(int idx=tin[child];idx<tout[child];idx++){
relax(idx,tin[p]);
}
for(int idx=tin[child];idx<tout[child];idx++){
add(idx);
}
}
}
relax(tin[p],tin[p]);
add(tin[p]);
}
}
return (ans==INF ? -1 : ans);
}
/*int main(){
ios::sync_with_stdio(0);
cin.tie(0);
}*/
