#include "race.h"
#include <bits/stdc++.h>
#define pb push_back
#define f first
#define sc second
using namespace std;
typedef long long int ll;
typedef string str;
const ll inf = 1e18;
ll k;
vector<set<pair<ll, int>>> s;
vector<vector<pair<int, ll>>> v;
ll ans = 1e18;
void dfs(int nd, int ss, ll dis, int depth){
for(auto [x, w]: v[nd]) if(x != ss) dfs(x, nd, dis+w, depth+1);
int mx = -1, in = -1;
for(auto [x, w]: v[nd]) if(x != ss){
if((int)s[x].size() > mx){
mx = s[x].size();
in = x;
}
}
if(in != -1) swap(s[nd], s[in]);
auto it = s[nd].lower_bound(make_pair(k+dis, 0));
if(it != s[nd].end() && it->f == k+dis) ans = min(ans, (ll)it->sc - depth);
for(auto [x, w]: v[nd]) if(x != ss){
for(auto [d, dpt]: s[x]){
dpt-=depth;
d-=dis;
ll dd = k-d;
if(dd == 0){
ans = min(ans, (ll)dpt);
}
else{
auto it = s[nd].lower_bound(make_pair(dd+dis, 0));
if(it != s[nd].end() && it->f == dd+dis){
ans = min(ans, dpt+(ll)(it->sc)-depth);
}
}
}
for(auto p: s[x]) s[nd].insert(p);
s[x].clear();
}
s[nd].insert({dis, depth});
}
int best_path(int n, int k, int edges[][2], int w[]){
::k = k;
v.resize(n);
s.resize(n);
for(int i = 0; i < n-1; i++){
v[edges[i][0]].pb({edges[i][1], w[i]});
v[edges[i][1]].pb({edges[i][0], w[i]});
}
dfs(0, -1, 0LL, 0);
if(ans == inf) ans = -1;
return ans;
}
