#include <bits/stdc++.h>
#include "race.h"
using namespace std;
const int N = 2e5 + 2;
vector<pair<int, long long> >G[N];
set<pair<long long, int> > s[N];
long long dist[N], edge[N], k;
long long ans;
///a + b - 2 * dist
void dfs (int nod, int p) {
s[nod].insert({dist[nod], edge[nod]});
for (auto it : G[nod]) {
if (it.first == p)
continue;
dist[it.first] = dist[nod] + it.second;
edge[it.first] = edge[nod] + 1;
dfs(it.first, nod);
if (s[nod].size() < s[it.first].size())
swap(s[nod], s[it.first]);
for (auto it2 : s[it.first]) {
auto meh = s[nod].lower_bound({k - it2.first + 2 * dist[nod], 0});
if (meh != s[nod].end() && meh->first + it2.first -2 * dist[nod] == k) {
ans = min(ans, it2.second + (*meh).second - 2 * edge[nod]);
}
}
for (auto it2 : s[it.first])
s[nod].insert(it2);
}
}
int best_path (int n, int K, int h[][2], int l[]) {
for (int i = 0; i < n - 1; i++) {
G[h[i][0]].push_back({h[i][1], l[i]});
G[h[i][1]].push_back({h[i][0], l[i]});
}
k = K;
ans = 1e9;
dfs(0, -1);
if (ans == 1e9)
return -1;
return ans;
}
