#include "race.h"
#include "bits/stdc++.h"
using namespace std;
const int N = 200001;
const int INF = 1e9;
int n , k , ans = INF;
vector < pair < int , int > > G[N];
void add_edge(int u,int v,int w){
G[u].push_back({v , w});
G[v].push_back({u , w});
}
int sub[N] , par[N];
bool is_rmv[N];
int gsz(int v , int p){
sub[v] = 1;
for(pair < int , int > nxt : G[v]){
int u = nxt.first;
if(u == p or is_rmv[u]) continue;
sub[v] += gsz(u , v);
}
return sub[v];
}
int find_centro(int v , int p , int need){
for(pair < int , int > nxt : G[v])
{
int u = nxt.first;
if(u == p or is_rmv[u] or sub[u] <= need / 2) continue;
return find_centro(u , v , need);
}
return v;
}
map < int , int > mn;
map < int , int > can;
vector < pair < int , int > > all;
void dfs(int v , int p , int nd , int wd , int centro)
{
all.push_back({nd , wd});
int need = k - wd;
if(can[need]) ans = min(ans , nd + mn[need]);
for(pair < int , int > nxt : G[v])
{
int u = nxt.first;
if(u != p && !is_rmv[u]) dfs(u , v , nd + 1 , wd + nxt.second , centro);
}
}
void build(int v)
{
int comp_sz = gsz(v , -1);
int centro = find_centro(v , -1 , comp_sz);
can.clear();
mn.clear();
can[0] = 1;
mn[0] = 0;
for(pair < int , int > nxt : G[centro])
{
all.clear();
int u = nxt.first;
if(!is_rmv[u])
{
dfs(u , -1 , 1 , nxt.second , centro);
for(pair < int , int > mnp : all)
{
int dsc = mnp.first;
int wg = mnp.second;
if(!can[wg])
{
can[wg] = 1;
mn[wg] = dsc;
}
else mn[wg] = min(mn[wg] , dsc);
}
}
}
is_rmv[centro] = 1;
for(pair < int , int > nxt : G[centro]){
int u = nxt.first;
if(!is_rmv[u]) build(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++) add_edge(H[i][0] , H[i][1] , L[i]);
build(0);
if(ans == INF) ans = -1;
return ans;
}
