#include "race.h"
#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef pair<int, int> pii;
#define X first
#define Y second
#define SZ(x) ll((x).size())
const ll MAXN = 2e5 + 10;
const ll INF = 1e18;
ll n , k , ans = INF , H[MAXN] , dist[MAXN];
vector<pii> adj[MAXN];
map<ll , ll> mn[MAXN];
void DFS(int v , int p = -1){
for(pii i : adj[v]){
int u = i.X , w = i.Y;
if(u == p) continue;
H[u] = H[v] + 1;
dist[u] = dist[v] + w;
DFS(u , v);
if(SZ(mn[u]) > SZ(mn[v])){
mn[v].swap(mn[u]);
}
for(auto &i : mn[u]){
if(i.Y == 0) continue;
ll D = k + dist[v] * 2 - i.X;
if(mn[v][D] != 0){
ans = min(ans , i.Y + mn[v][D] - 2 * H[v]);
}
}
for(auto &i : mn[u]){
if(i.Y == 0) continue;
if(mn[v][i.X] == 0) mn[v][i.X] = i.Y;
mn[v][i.X] = min(mn[v][i.X] , i.Y);
}
}
ll D = k + dist[v];
if(mn[v][D] != 0){
ans = min(ans , mn[v][D] - H[v]);
}
if(mn[v][dist[v]] == 0) mn[v][dist[v]] = H[v];
mn[v][dist[v]] = min(mn[v][dist[v]] , H[v]);
}
int best_path(int N, int K, int H[][2], int L[]){
n = N; k = K;
for(int i = 0 ; i + 1 < n ; i++){
int v = H[i][0] , u = H[i][1] , w = L[i];
adj[v].push_back({u , w});
adj[u].push_back({v , w});
}
DFS(0);
return (ans == INF ? -1 : ans);
}
