#include "race.h"
#include<bits/stdc++.h>
using namespace std;
const int N = 2e5+4;
const int inf = 1e9;
struct Cd{
vector<pair<int,int>> adj[N];
int vis[N],sz[N],up[N],mn[5*N];
int ans,k;
void init(int _k){
for (int i=0; i<5*N; i++) mn[i] = inf;
ans = inf; k = _k;
}
int find(int u,int p,int Sz){
sz[u] = 1;
int val = 0, x = 0;
for (auto [v, w] : adj[u]) if (v != p && !vis[v]){
x ^= find(v, u, Sz); sz[u] += sz[v];
val = max(val, sz[v]);
}
if (max(val, Sz-sz[u]) <= Sz/2) up[x = u] = p;
return x;
}
void dfs(int u,int p,int dis,int h,int f){
if (dis > k) return;
if (f == 0) ans = min(ans, mn[k-dis]+h);
if (f == 1) mn[dis] = min(mn[dis], h);
if (f == 2) mn[dis] = inf;
for (auto [v, w] : adj[u]) if (v != p && !vis[v])
dfs(v, u, dis+w, h+1, f);
}
void calc(int u){
mn[0] = 0;
for (auto [v, w] : adj[u]) if (!vis[v]){
dfs(v, u, w, 1, 0);
dfs(v, u, w, 1, 1);
}
dfs(u, -1, 0, 0, 2);
}
void build(int u,int Sz){
u = find(u, -1, Sz);
if (up[u] != -1) sz[up[u]] = Sz-sz[u];
vis[u] = 1; calc(u);
for (auto [v, w] : adj[u]) if (!vis[v])
build(v, sz[v]);
}
} d;
int best_path(int n, int k, int H[][2], int L[]){
for (int i=0; i<n-1; i++){
d.adj[H[i][0]+1].push_back({H[i][1]+1, L[i]});
d.adj[H[i][1]+1].push_back({H[i][0]+1, L[i]});
}
d.init(k);
d.build(1, n);
return (d.ans == inf ? -1 : d.ans);
}
/*
int main(){
int n,k,H[N][2],L[N]; cin >> n >> k;
for (int i=0; i<n-1; i++) cin >> H[i][0] >> H[i][1] >> L[i];
cout << best_path(n, k, H, L) << "\n";
return 0;
}
*/
