//In the name of God
#include "race.h"
#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
const ll maxn = 2e5 + 100;
const ll mod = 1e9 + 7;
const int inf = 1e9;
const ll INF = 1e18;
#define fast_io ios::sync_with_stdio(false);cin.tie(0);cout.tie(0);
#define file_io freopen("input.txt", "r+", stdin);freopen("output.txt", "w+", stdout);
#define pb push_back
#define Mp make_pair
#define F first
#define S second
#define Sz(x) ll((x).size())
#define all(x) (x).begin(), (x).end()
int n, k, d[maxn];
ll s[maxn], s2[maxn];
vector<pii> g[maxn];
map<ll, ll> mn[maxn];
ll ans = INF;
void dfs(int v, int p = -1){
mn[v][0] = d[v];
for(pii e : g[v]){
int u = e.F;
int c = e.S;
if(u == p) continue;
d[u] = d[v] + 1;
dfs(u, v);
s[u] += c;
if(Sz(mn[v]) < Sz(mn[u])){
mn[v].swap(mn[u]);
swap(s[v], s[u]);
}
for(pll i : mn[u]){
i.F += s[u];
if(mn[v].find(k - i.F - s[v]) != mn[v].end()){
ans = min(ans, i.S + mn[v][k - i.F - s[v]] - d[v] * 2);
}
}
for(pll i : mn[u]){
i.F += s[u];
if(mn[v].find(i.F - s[v]) == mn[v].end()){
mn[v][i.F - s[v]] = i.S;
}
else mn[v][i.F - s[v]] = min(mn[v][i.F - s[v]], i.S);
}
}
return;
}
int best_path(int N, int K, int H[][2], int L[]){
n = N;
k = K;
for(int i = 0; i < n - 1; i++){
int v = H[i][0], u = H[i][1];
g[v].pb(Mp(u, L[i]));
g[u].pb(Mp(v, L[i]));
}
dfs(0);
if(ans == INF) return -1;
return ans;
}
