#include "race.h"
#include <bits/stdc++.h>
using namespace std;
#define MOD1 1000000007
#define MOD2 998244353
#define fir first
#define sec second
#define pushf push_front
#define pushb push_back
#define popf pop_front
#define popb pop_back
#define mp make_pair
#define all(a) a.begin(), a.end()
#define lbound(v, x) lower_bound(all(v), x) - v.begin()
#define ubound(v, x) upper_bound(all(v), x) - v.begin()
#define chmax(a, b) a = max(a, b)
#define chmin(a, b) a = min(a, b);
#define FOR1(a) for (int _ = 0; _ < (a); ++_)
#define FOR2(i, a) for (int i = 0; i < (a); ++i)
#define FOR3(i, a, b) for (int i = (a); i < (b); ++i)
#define RFOR1(a) for (int _ = (a)-1; _ >= 0; --_)
#define RFOR2(i, a) for (int i = (a)-1; i >= 0; --i)
#define RFOR3(i, a, b) for (int i = (b)-1; i >= (a); --i)
#define overload3(a, b, c, d, ...) d
// Always choose the fourth argument to call. Hence, which function to call is determined by the number of given arguments.
#define REP(...) overload3(__VA_ARGS__, FOR3, FOR2, FOR1)(__VA_ARGS__)
#define RREP(...) overload3(__VA_ARGS__, RFOR3, RFOR2, RFOR1)(__VA_ARGS__)
typedef long long ll;
typedef pair<int, int> pii;
typedef vector<int> vi;
typedef pair<ll, ll> pll;
typedef vector<ll> vll;
typedef vector<bool> vb;
typedef vector<char> vc;
typedef vector<string> vs;
typedef vector<pii> vpii;
typedef vector<pll> vpll;
typedef vector<vi> vvi;
typedef vector<vll> vvll;
typedef vector<vb> vvb;
typedef vector<vc> vvc;
typedef vector<vpii> vvpii;
typedef vector<vpll> vvpll;
typedef queue<int> qi;
typedef queue<ll> qll;
typedef queue<pii> qpii;
typedef queue<pll> qpll;
typedef deque<int> dqi;
typedef deque<ll> dqll;
typedef deque<pii> dqpii;
typedef deque<pll> dqpll;
typedef priority_queue<int> pqi;
typedef priority_queue<ll> pqll;
typedef priority_queue<pii> pqpii;
typedef priority_queue<pll> pqpll;
typedef priority_queue<int, vi, greater<int> > r_pqi;
typedef priority_queue<ll, vll, greater<ll> > r_pqll;
typedef priority_queue<pii, vpii, greater<pii> > r_pqpii;
typedef priority_queue<pll, vpll, greater<pll> > r_pqpll;
const int INF = 1e8;
const int maxn = 2e5+5, maxk = 1e6+5;
int k, mx;
int ans = INF;
vpii adj[maxn];
int sub_size[maxn];
int len[maxk];
bool removed[maxn];
int get_sub_size(int u, int par = 0) {
sub_size[u] = 1;
for (auto [v, w] : adj[u]) {
if (v == par || removed[v]) {
continue;
}
sub_size[u] += get_sub_size(v, u);
}
return sub_size[u];
}
int get_centr(int u, int tree_size, int par = 0) {
for (auto [v, w] : adj[u]) {
if (v == par || removed[v]) {
continue;
}
if (sub_size[v] * 2 > tree_size) {
return get_centr(v, tree_size, u);
}
}
return u;
}
void get_dists(int u, bool fil, int par, int depth, int cnt = 1) {
if(depth > k) {
return;
}
if(fil) {
// cerr<<depth<<' '<<cnt<<endl;
chmin(len[depth], cnt);
}
else {
if(len[k - depth] < INF) {
// cerr<<depth<<' '<<k<<' '<<len[k - depth]<<endl;
chmin(ans, cnt + len[k - depth]);
}
}
chmax(mx, depth);
for (auto [v, w] : adj[u]) {
if (v == par || removed[v]) {
continue;
}
get_dists(v, fil, u, depth + w, cnt + 1);
}
return;
}
// build centr tree
void build(int u) {
int centr = get_centr(u, get_sub_size(u));
/*
* For all nodes in the subtree rooted at `centr`, calculate their
* distances to the centr
*/
mx = 0;
removed[centr] = true;
for (auto [v, w] : adj[centr]) {
if (removed[v]) {
continue;
}
get_dists(v, 0, centr, w);
get_dists(v, 1, centr, w);
}
fill(len+1, len + mx + 1, INF);
for (auto [v, w] : adj[centr]) {
if (removed[v]) {
continue;
}
build(v);
}
}
int best_path(int n, int K, int H[][2], int L[])
{
k = K;
REP(i, n-1) {
int a = H[i][0], b = H[i][1], c = L[i];
adj[a].pushb(mp(b, c));
adj[b].pushb(mp(a, c));
}
memset(removed, 0, sizeof(removed));
fill(len, len+maxk, INF);
len[0] = 0;
build(0);
if(ans >= INF) {
ans = -1;
}
return ans;
}
// #define MAX_N 500000
// static int N, K;
// static int H[MAX_N][2];
// static int L[MAX_N];
// static int solution;
// inline
// void my_assert(int e) {if (!e) abort();}
// void read_input()
// {
// int i;
// my_assert(2==scanf("%d %d",&N,&K));
// for(i=0; i<N-1; i++)
// my_assert(3==scanf("%d %d %d",&H[i][0],&H[i][1],&L[i]));
// my_assert(1==scanf("%d",&solution));
// }
// int main()
// {
// int ans;
// read_input();
// ans = best_path(N,K,H,L);
// if(ans==solution)
// printf("Correct.\n");
// else
// printf("Incorrect. Returned %d, Expected %d.\n",ans,solution);
// return 0;
// }
