#include<bits/stdc++.h>
#include "race.h"
using namespace std;
const int N = 2e5+37;
int mi = 1e7, n, k, p;
vector<array<int, 2>> adj[N];
vector<int> s(N), vis2(N);
vector<int> best((int)1e6+37, 1e7);
vector<array<int, 2>> mp;
vector<int> pff;
void dfs(int v, int p){
int pf=0;
s[v] = 1;
for(auto i: adj[v]){
if(vis2[i[0]]||i[0]==p) continue;
pf++;
dfs(i[0], v); s[v]+=s[i[0]];
}
}
int dfs2(int v, int p, int gh){
for(auto i: adj[v]){
if(vis2[i[0]]||i[0]==p) continue;
if(s[i[0]]>=gh/2) return dfs2(i[0], v, gh);
}
return v;
}
void dfs3(int v, int dist, int z, int p){
// cout<<v<<" "<<dist<<" "<<z<<"\n";
if(dist<=k){
mp.push_back({dist, z});
for(auto i: adj[v]){
if(vis2[i[0]]||i[0]==p) continue;
dfs3(i[0], dist+i[1], z+1, v);
}
}
}
void dfs4(int v){
for(auto pf: adj[v]){
if(vis2[pf[0]]) continue;
mp.clear();
dfs3(pf[0], pf[1], 1, v);
for(auto i: mp){
if(i[0]>k) continue;
if(best[k-i[0]]!=1e7){
mi=min(mi, i[1]+best[k-i[0]]);
}
}
for(auto i: mp){
if(i[0]<=k){
best[i[0]]=min(i[1], best[i[0]]);
pff.push_back(i[0]);
}
}
}
}
void gh(int v){
dfs(v, v);
int x = dfs2(v, v, s[v]);
dfs4(x);
for(auto i:pff) if(i<=k)best[i]=1e7;
pff.clear();
vis2[x]=1; best[0]=0;
for(auto i: adj[x]){
if(!vis2[i[0]]) gh(i[0]);
}
}
int best_path(int N, int K, int a[][2], int l[])
{
best[0]=0;
n = N, k = K;
for(int i= 0; i < n-1; i++){
int x=a[i][0], y=a[i][1], z=l[i];
adj[x].push_back({y, z});
adj[y].push_back({x, z});
}
p=1;
gh(0);
if(mi==1e7) return -1;
return mi;
}
void f(){
#ifndef ONLINE_JUDGE
freopen("in.txt", "r", stdin);
freopen("out.txt", "w", stdout);
#endif
}
/*
signed main()
{
f();
int n, k; cin >> n >> k;
int a[n-1][2], l[n-1];
for(int i=0; i<n-1; i++){
cin>>a[i][0]>>a[i][1] >> l[i];
}
cout<< best_path(n, k, a, l);
cerr<<(float)clock()/CLOCKS_PER_SEC;
}
*/
