#include <bits/stdc++.h>
#include "race.h"
#define TASK "race"
#define INT_LIM (int) 2147483647
#define LL_LIM (long long) 9223372036854775807
#define endl '\n'
#define mp make_pair
#define pb push_back
#define fi first
#define se second
#define BIT(i,x) (((i)>>(x))&1)
#define FOR(i,a,b) for(int i = (a); i<=(b); i++)
#define FORD(i,a,b) for(int i = (a); i>=(b); i--)
#define ll long long
#define pii pair<int,int>
using namespace std;
///------------------------------------------///
int n,k, ans = INT_LIM;
vector<pii> adj[200005];
bool dis[200005];
int sz[200005];
void initsize(int u, int p)
{
sz[u] = 1;
for (auto V:adj[u]) if (V.fi!=p && !dis[V.fi])
{
initsize(V.fi, u);
sz[u]+= sz[V.fi];
}
}
int findcentroid(int u, int p, int n)
{
for (auto V:adj[u]) if (V.fi!=p && !dis[V.fi] && sz[V.fi]>n/2)
{
return findcentroid(V.fi, u, n);
}
return u;
}
map<int,int> f;
void dfs(int u, int p, int deep, int d, bool upd)
{
if (d>k) return;
if (!upd)
{
if (f.find(k-d)!=f.end())
{
ans = min(ans, f[k-d]+deep);
}
}
else
{
if (f.find(d)!=f.end()) f[d] = min(f[d], deep);
else f[d] = deep;
}
for (auto V:adj[u]) if (V.fi!=p && !dis[V.fi])
{
int v = V.fi, w = V.se;
dfs(v, u, deep+1, d+w, upd);
}
}
void process(int u)
{
f.clear();
f[0] = 0;
for (auto V:adj[u]) if (!dis[V.fi])
{
int v = V.fi, w = V.se;
dfs(v, u, 1, w, 0);
dfs(v, u, 1, w, 1);
}
}
void decompose(int u)
{
initsize(u, -1);
u = findcentroid(u, -1, sz[u]);
process(u);
dis[u] = true;
for (auto V:adj[u]) if (!dis[V.fi])
{
decompose(V.fi);
}
}
int best_path(int N, int K, int h[][2], int l[])
{
n = N; k = K;
FOR(i, 0, n-2)
{
int u = h[i][0]+1, v = h[i][1]+1;
adj[u].pb(mp(v,l[i]));
adj[v].pb(mp(u,l[i]));
}
decompose(1);
if (ans==INT_LIM) return -1;
return ans;
}
