#include<bits/stdc++.h>
#include "race.h"
using namespace std;
const int maxn=2e5+10;
struct c
{
int x,t;
};
vector<c> v[maxn];
int n,k;
long long d[maxn];
int r[maxn];
map<long long,int> m[maxn];
int ans=1e9;
void dfs1(int i,int par)
{
r[i]=r[par]+1;
for(auto nb:v[i])
{
if(nb.x==par)
{
continue;
}
d[nb.x]=d[i]+nb.t;
dfs1(nb.x,i);
}
}
void unite(int x,int y)
{
if(m[x].size() < m[y].size())
swap(m[x], m[y]);
for(auto [key,value] : m[y])
{
long long need = k - key + 2*d[x];
if(m[x].count(need))
ans = min(ans, m[x][need] + value - 2*r[x]);
}
for(auto [key,value] : m[y])
{
if(!m[x].count(key))
m[x][key] = value;
else
m[x][key] = min(m[x][key], value);
}
}
//k=d[u]+d[v]-2*d[lca(x,y)]
void dfs(int i,int par)
{
for(auto nb:v[i])
{
if(nb.x==par)
{
continue;
}
//cout<<i<<' '<<nb.x<<' '<<"||"<<endl;
dfs(nb.x,i);
unite(i,nb.x);
}
}
int best_path(int N,int K,int h[][2],int l[])
{
n=N;
k=K;
for(int i=0; i<n-1; i++)
{
//cout<<h[i][0]<<' '<<h[i][1]<<' '<<l[i]<<endl;
v[h[i][0]].push_back({h[i][1],l[i]});
v[h[i][1]].push_back({h[i][0],l[i]});
}
r[0]=-1;
dfs1(0,0);
for(int i=0; i<n; i++)
{
//cout<<d[i]<<' '<<r[i]<<endl;
m[i][d[i]]=r[i];
}
dfs(0,0);
if(ans==1e9)
{
return -1;
}
return ans;
}
/*
11 12
0 1 3
0 2 4
2 3 5
3 4 4
4 5 6
0 6 3
6 7 2
6 8 5
8 9 6
8 10 7
*/
