/*
Take me to church
I'll worship like a dog at the shrine of your lies
I'll tell you my sins and you can sharpen your knife
Offer me that deathless death
Good God, let me give you my life
*/
#include<bits/stdc++.h>
#include "race.h"
#define x first
#define y second
using namespace std;
const int N = 200005, MXK = 2000006;
int n, k, Mn = N, M[N], SZ[N], qu[N], H[N], D[N], B[MXK];
vector < pair < int , int > > Adj[N];
vector < int > A;
void DFSSZ(int v, int p = -1)
{
SZ[v] = 1;
for (auto u : Adj[v])
if (!M[u.x] && u.x != p)
DFSSZ(u.x, v), SZ[v] += SZ[u.x];
}
inline int Centroid(int v)
{
DFSSZ(v);
int _n = SZ[v], w = 1, p = -1;
while (w)
{
w = 0;
for (auto u : Adj[v])
if (!M[u.x] && u.x != p && SZ[u.x] * 2 > _n)
{p = v; v = u.x; w = 1; break;}
}
return (v);
}
void DFS(int v, int p)
{
A.push_back(v);
if (D[v] <= k)
Mn = min(Mn, H[v] + B[k - D[v]]);
for (auto u : Adj[v])
if (!M[u.x] && u.x != p)
H[u.x] = H[v] + 1, D[u.x] = min(D[v] + u.y, MXK - 2), DFS(u.x, v);
}
void UNDFS(int v, int p)
{
B[D[v]] = B[MXK - 1];
for (auto u : Adj[v])
if (!M[u.x] && u.x != p)
UNDFS(u.x, v);
}
inline void Solve(int v)
{
H[v] = D[v] = 0;
for (auto u : Adj[v])
if (!M[u.x])
{
H[u.x] = H[v] + 1;
D[u.x] = D[v] + u.y;
DFS(u.x, v);
for (int w : A)
B[D[w]] = min(B[D[w]], H[w]);
A.clear();
}
for (auto u : Adj[v])
if (!M[u.x])
UNDFS(u.x, v);
}
inline void Decompose()
{
int l = 0, r = 0;
qu[r ++] = 0;
while (r - l)
{
int v = Centroid(qu[l ++]);
Solve(v); M[v] = 1;
for (auto u : Adj[v])
if (!M[u.x])
qu[r ++] = u.x;
}
}
int best_path(int _n, int _k, int _E[200000][2], int _L[200000])
{
n = _n; k = _k;
//cin >> n >> k;
memset(B, 63, sizeof(B)); B[0] = 0;
for (int i = 0; i < n - 1; i ++)
{
Adj[_E[i][0]].push_back({_E[i][1], _L[i]});
Adj[_E[i][1]].push_back({_E[i][0], _L[i]});
//int a, b, c;
//cin >> a >> b >> c;
//Adj[a].push_back({b, c});
//Adj[b].push_back({a, c});
}
int l = 0, r = 0;
Decompose();
if (Mn == N)
Mn = -1;
//printf("%d\n", Mn);
//return 0;
return (Mn);
}
