#include "race.h"
#include <bits/stdc++.h>
// #define int long long
#define F first
#define S second
#define all(x) x.begin(), x.end()
#define kill(x) cout << x << endl, exit(0);
#define mp make_pair
#define pii pair<ll, ll>
#define pb push_back
using namespace std;
typedef long long ll;
const int MAXN = (int)1e6 + 7;
const int MOD = 998244353;
const int INF = (int)1e9 + 7;
ll n, m, t, u, v, w, tmp, tmp2, tmp3, tmp4, ans, k;
ll arr[MAXN], cost[MAXN], sz[MAXN];
pii love[MAXN];
bool hate[MAXN];
vector<pii> adj[MAXN];
void DFSsz(int v, int p=-1) {
sz[v] = 1;
for (auto cur:adj[v]) {
int u = cur.F, w = cur.S;
if (!hate[u] && u != p) {
DFSsz(u, v);
sz[v] += sz[u];
}
}
}
int centroid(int tot, int v, int p=-1) {
for (auto cur:adj[v]) {
int u = cur.F, w = cur.S;
if (u != p && !hate[u] && 2*sz[u] > tot) return centroid(tot, u, v);
}
return v;
}
void check_mol(int v, int cent, int p, pii dis, bool x) {
if (dis.S > k) return;
for (auto cur:adj[v]) {
int u = cur.F, w = cur.S;
if (u != p && !hate[u]) check_mol(u, cent, v, mp(dis.F+1, dis.S+w), x);
}
if (!x) {
if (love[k-dis.S].F == cent) {
ans = min(ans, dis.F+love[k-dis.S].S);
}
} else {
if (love[dis.S].F != cent) {
love[dis.S].F = cent;
love[dis.S].S = dis.F;
} else {
love[dis.S].S = min(love[dis.S].S, dis.F);
}
}
}
void solve(int v) {
DFSsz(v);
int cent = centroid(sz[v], v);
for (auto cur:adj[cent]) {
int u = cur.F, w = cur.S;
if (hate[u]) continue;
check_mol(u, cent, cent, mp(1, w), 0);
check_mol(u, cent, cent, mp(1, w), 1);
}
if (love[k].F == cent) ans = min(ans, love[k].S);
hate[cent] = 1;
for (auto cur:adj[cent]) if (!hate[cur.F]) solve(cur.F);
}
int best_path(int N, int K, int H[][2], int L[]) {
n = N, k=K;
for (int i=0; i<n-1; i++) {
u = H[i][0];
v = H[i][1];
w = L[i];
u++, v++;
adj[u].pb(mp(v, w));
adj[v].pb(mp(u, w));
}
ans = INF;
solve(1);
if (ans == INF) return -1;
return ans;
}
