#include "race.h"
#include<iostream>
#include<vector>
#include<queue>
#include<deque>
#include<string>
#include<fstream>
#include<algorithm>
#include <iomanip>
#include<map>
#include <set>
#include <unordered_map>
#include <stack>
#include <unordered_set>
#include <cmath>
#include <cstdint>
#define shit short int
#define ll long long
#define For(i, n) for(int i = 0; i < (int)n; i++)
#define ffor(i, a, n) for(int i = (int)a; i < (int)n; i++)
#define rfor(i, n) for(int i = (int)n; i >= (int)0; i--)
#define rffor(i, a, n) for(int i = (int)n; i >= (int)a; i--)
#define vec vector
#define ff first
#define ss second
#define pb push_back
#define pii pair<int, int>
#define NEK 1000000000
#define mod 1000000007
#define mod2 1000000009
#define rsz resize
#define prv1 43
#define prv2 47
#define D 8
#define trav(a,x) for (auto& a: x)
#define pb push_back
#define ub upper_bound
#define lb lower_bound
#define sig 0.0000001
using namespace std;
vec<vec<pii>> g;
vec<int> pod;
int n, k;
vec<bool> je;
int pods(int x, int pr = -1) {
pod[x] = 1;
for(auto&i : g[x]) {
if (i.ff == pr) continue;
if (je[i.ff]) continue;
pod[x] += pods(i.ff, x);
}
return pod[x];
}
int centroid(int x, int vel, int pr = -1) {
for (auto i : g[x]) {
if (i.ff == pr) continue;
if (je[i.ff]) continue;
if (pod[i.ff] * 2 > vel) return centroid(i.ff, vel, x);
}
return x;
}
int mini = -1;
void dfs(int x, vec<pii>& h, int pr, int d, int dh) {
h.push_back({ d, dh });
for (auto&i : g[x]) {
if (i.ff == pr) continue;
if (je[i.ff]) continue;
dfs(i.ff, h, x, d + i.ss, dh + 1);
}
return;
}
void ries(int x) {
pods(x);
int c = centroid(x, pod[x]);
unordered_map<int, int> umap;
umap[0] = 0;
for (auto i : g[c]) {
if (je[i.ff]) continue;
vec<pii> h;
dfs(i.ff, h, c, i.ss, 1);
for (auto j : h) {
if (umap.find(k - j.ff) != umap.end()) {
mini = min(mini, umap[k - j.ff] + j.ss);
}
}
for (auto j : h) {
if (umap.find(j.ff) == umap.end()) {
umap[j.ff] = j.ss;
}
umap[j.ff] = min(umap[j.ff], j.ss);
}
}
je[c] = 1;
for (auto i : g[c]) {
if (je[i.ff]) continue;
ries(i.ff);
}
}
int best_path(int n1, int k1, int h[][2], int l[]) {
n = n1; k = k1;
mini = n + 1;
g.resize(n);
pod.resize(n);
je.resize(n, false);
For(i, n-1) {
g[h[i][0]].push_back({ h[i][1], l[i] });
g[h[i][1]].push_back({ h[i][0], l[i] });
}
ries(0);
if (mini == (n + 1)) mini = -1;
return mini;
}
