#include "race.h"
#include <bits/stdc++.h>
#define ll long long
#define F first
#define S second
using namespace std;
int ans=1e9;
ll k;
vector<pair<int,ll>>adj[200005];
ll dep[200005];
int dis[200005];
map<int,int> arr[200005];
void dfs(int u,int p)
{
for(auto x:adj[u])
{
if(x.F!=p)
{
dep[x.F]=dep[u]+x.S;
dis[x.F]=dis[u]+1;
dfs(x.F,u);
if(arr[x.F].size()>arr[u].size())
swap(arr[x.F],arr[u]);
for(auto f:arr[x.F])
{
ll z=2;
z*=dep[u];
z+=k-f.F;
if(arr[u][z])
{
ans=min(ans,arr[u][z]+f.S-2*dis[u]);
}
}
for(auto g:arr[x.F])
{
if(arr[u][g.F])
arr[u][g.F]=min(arr[u][g.F],g.S);
else
arr[u][g.F]=g.S;
}
}
}
if(arr[u].count(dep[u]+k))
ans=min(ans,arr[u][dep[u]+k]-dis[u]);
arr[u][dep[u]]=dis[u];
}
int best_path(int N, int K, int H[][2], int L[])
{
k=K;
for(int i=0;i<N-1;i++)
{
adj[H[i][0]].push_back({H[i][1], L[i]});
adj[H[i][1]].push_back({H[i][0], L[i]});
}
dfs(0,0);
if(ans==1e9)
ans=-1;
return ans;
}
