#include <bits/stdc++.h>
using namespace std;
#define all(x) (x).begin(), (x).end()
#define ll long long int
#define pii pair <ll, int>
#define pb push_back
#define ff first
#define ss second
const int N = 2e5+5;
const int MAXN = 1e6+5;
const int inf = 1e9;
int P[MAXN];
int sub[N], rem[N], tp[N], dpt[N];
ll w[N];
int answer = inf;
vector<pii> E[N], G[N];
vector<int> nodes;
void solve(vector<int> nodes, int T, int K){
for (auto i : nodes){
G[tp[i]].pb({w[i], dpt[i]});
}
for (int i = 1; i <= T; i++){
for (auto j : G[i]){
if (j.ff <= K)
answer = min(answer, P[K-j.ff]+j.ss);
}
for (auto j : G[i]){
if (j.ff <= K) P[j.ff] = min(P[j.ff], j.ss);
}
G[i].clear();
}
for (auto i : nodes) if (w[i] <= K) P[w[i]] = inf;
}
void dfs(int nd, int pr){
sub[nd] = 1;
for (auto i : E[nd]){
if (i.ff == pr or rem[i.ff]) continue;
dfs(i.ff, nd);
sub[nd] += sub[i.ff];
}
}
int centroid(int nd, int pr, int sz){
for (auto i : E[nd]){
if (i.ff == pr or rem[i.ff]) continue;
if (sub[i.ff]*2 > sz) return centroid(i.ff, nd, sz);
}
return nd;
}
void F(int nd, int pr, ll W, int lvl, int T){
nodes.pb(nd);
w[nd] = W;
dpt[nd] = lvl;
tp[nd] = T;
for (auto i : E[nd]){
if (i.ff == pr or rem[i.ff]) continue;
F(i.ff, nd, W+i.ss, lvl+1, T);
}
}
void build(int nd, int pr, int K){
int centr = centroid(nd, 0, sub[nd]);
rem[centr] = 1;
nodes.clear();
int T = 0;
for (auto i : E[centr]){
if (rem[i.ff]) continue;
F(i.ff, 0, i.ss, 1, ++T);
}
solve(nodes, T, K);
for (auto i : E[centr]){
if (rem[i.ff]) continue;
dfs(i.ff, 0);
build(i.ff, centr, K);
}
}
int best_path(int n, int k, int H[][2], int L[]){
for (int i = 0; i < n-1; i++){
E[H[i][0]+1].pb({H[i][1]+1, L[i]});
E[H[i][1]+1].pb({H[i][0]+1, L[i]});
}
P[0] = 0;
for (int i = 1; i <= k; i++) P[i] = inf+7;
dfs(1, 0);
build(1, 0, k);
if (answer > n) answer = -1;
return answer;
}
// int main ()
// {
// ios::sync_with_stdio(false);
// cin.tie(0);
// int n, k;
// cin >> n >> k;
// int H[n][2], L[n];
// for (int i = 0; i < n-1; i++){
// cin >> H[i][0] >> H[i][1] >> L[i];
// }
// cout << best_path(n, k, H, L);
// }
