#include <bits/stdc++.h>
using namespace std;
#pragma GCC optimize("O3")
#pragma GCC optimize("unroll-loops")
#pragma GCC target("avx2")
#define fi first
#define se second
#define ll long long
#define pb push_back
#define ii pair<int,int>
#define MAX_N 500000
const int nax=2e5+5;
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
vector<pair<int,int>> adj[nax];
int sz[nax];
bool removed[nax];
vector<vector<pair<ll,pair<ll,int>>>> dist(nax);
vector<map<int,vector<pair<int,int>>>> mp(nax);
set<int> st[nax];
int get_tree_size(int x,int p){
sz[x]=1;
for(auto u:adj[x]){
if(u.fi==p||removed[u.fi]) continue;
sz[x]+=get_tree_size(u.fi,x);
}
return sz[x];
}
int get_centroid(int x,int t_sz,int p){
for(auto u:adj[x]){
if(u.fi==p||removed[u.fi]) continue;
if(sz[u.fi]*2>t_sz){
return get_centroid(u.fi,t_sz,x);
}
}
return x;
}
void get_dist(int x,int centroid,int p,pair<ll,int> cur){
for(auto u:adj[x]){
if(u.fi==p||removed[u.fi]) continue;
cur.fi+=u.se;
cur.se++;
get_dist(u.fi,centroid,x,cur);
cur.fi-=u.se;
cur.se--;
}
//cout <<x<<" "<<centroid<<" "<<cur.fi<<" "<<cur.se<<endl;
mp[centroid][cur.fi].pb({x,cur.se});
dist[x].pb({centroid,cur});
st[x].insert(centroid);
}
void build(int x){
int centroid=get_centroid(x,get_tree_size(x,-1),-1);
for(auto u:adj[centroid]){
if(removed[u.fi]) continue;
get_dist(u.fi,centroid,centroid,make_pair(u.se,1));
}
removed[centroid]=true;
for(auto u:adj[centroid]){
if(removed[u.fi]) continue;
build(u.fi);
}
}
int n,k;
int query(int x){
int ans=1e9;
if(mp[x].count(k)){
for (int i = 0; i < mp[x][k].size(); ++i)
{
ans=min(ans,mp[x][k][i].se);
}
}
for(int u=0;u<dist[x].size();u++){
for (int i = 0; i < (int)mp[dist[x][u].fi][k-dist[x][u].se.fi].size(); ++i)
{
if(mp[dist[x][u].fi][k-dist[x][u].se.fi][i].fi==x) continue;
if(u<dist[x].size()-1&&st[mp[dist[x][u].fi][k-dist[x][u].se.fi][i].fi].count(dist[x][u+1].fi)||dist[x][u+1].fi==mp[dist[x][u].fi][k-dist[x][u].se.fi][i].fi||st[mp[dist[x][u].fi][k-dist[x][u].se.fi][i].fi].count(x)) continue;
ans=min(ans,dist[x][u].se.se+mp[dist[x][u].fi][k-dist[x][u].se.fi][i].se);
//cout <<" "<<x<<" "<<dist[x][u].fi<<" "<<mp[dist[x][u].fi][k-dist[x][u].se.fi][i].fi<<" "<<ans<<endl;
}
}
return ans;
}
int best_path(int N, int K, int H[][2], int L[])
{
n=N;
k=K;
for (int i = 0; i < n-1; ++i)
{
adj[H[i][0]].pb({H[i][1],L[i]});
adj[H[i][1]].pb({H[i][0],L[i]});
}
build(0);
int ans=1e9;
for (int i = 0; i < n; ++i)
{
int cur=query(i);
ans=min(ans,cur);
}
if(ans==1e9) return -1;
else return ans;
}
