#include "race.h"
#include<bits/stdc++.h>
#define FOR(i,a) for(int i=0;i<a;i++)
#define FOR1(i,a) for(int i=1;i<=a;i++)
#define db(a) printf("<%d> ",a)
#define f first
#define s second
#define all(x) x.begin(),x.end()
#define mp make_pair
#define pb emplace_back
#define p emplace
#define ii pair<int,int>
#define ll long long
#define rf() freopen("_working/input.in","r",stdin)
#define pf() freopen("_working/output.out","w+",stdout)
using namespace std;
const int INF=1e9;
int size[200005];
queue<ii> len;
set<ii> edge[200005];
int ans = INF;
int centroid(int u,int p,int n){
for(auto v:edge[u]){
if(v.f!=p && size[v.f]>n/2)return centroid(v.f,u,n);
}
return u;
}
void dfs(int u,int p){
size[u]=1;
for(auto v:edge[u]){
if(v.f!=p){
dfs(v.f,u);
size[u]+=size[v.f];
}
}
}
void setlen(int u,int p,int l,int cnt,int cen){
if(l>1000000)return;
len.p(l,cnt);
for(auto v:edge[u]){
if(v.f!=p){
setlen(v.f,u,l+v.s,cnt+1,cen);
}
}
}
int k;
int decomp(int u,int p){
set<ii> f,tmp;
dfs(u,-1);
int x = centroid(u,-1,size[u]);
for(auto v:edge[x]){
setlen(v.f,x,v.s,1,x);
while(!len.empty()){
tmp.p(len.front());
auto x = f.upper_bound(mp(k-len.front().f,-1));
if(x->f == k-len.front().f)ans = min(ans,x->s+len.front().s);
len.pop();
}
for(auto i:tmp){
f.insert(i);
}
tmp.clear();
}
for(auto v:edge[x]){
edge[v.f].erase(mp(x,v.s));
decomp(v.f,x);
}
edge[x].clear();
return x;
}
int best_path(int N, int K, int H[][2], int L[])
{
k=K;
for(int i=0;i<N-1;i++){
edge[H[i][0]].p(H[i][1],L[i]);
edge[H[i][1]].p(H[i][0],L[i]);
}
decomp(0,-1);
return ans==1e9?-1:ans;
}
