#include "race.h"
#include<bits/stdc++.h>
using namespace std;
vector<pair<int,int> >adj[200005];
int sz[200005];
int used[200005];
long long cnt[1000005];
int inf=1e9;
long long ans=inf;
vector<pair<int,long long> >v[200005];
int n,k;
int dfssz(int u,int p=-1){
sz[u]=1;
for(auto x:adj[u])if(!used[x.first]&&x.first!=p)sz[u]+=dfssz(x.first,u);
return sz[u];
}
int centroid(int u,int rsz,int p=-1){
for(auto x:adj[u])if(!used[x.first]&&x.first!=p&&sz[x.first]>rsz/2)return centroid(x.first,rsz,u);
return u;
}
void dfs1(int u,int d,int l,int rt,int p=-1){
if(d<=k)v[rt].push_back({d,l});else return;
for(auto x:adj[u])if(!used[x.first]&&x.first!=p)dfs1(x.first,d+x.second,l+1,rt,u);
}
void decom(int u){
u=centroid(u,dfssz(u));
//cerr<<"u:"<<u<<endl;
used[u]=1;
for(auto x:adj[u])if(!used[x.first]){
dfs1(x.first,x.second,1,x.first);
for(auto d:v[x.first])if(d.first<=k)ans=min(ans,cnt[k-d.first]+d.second);
for(auto d:v[x.first])if(d.first<=k)cnt[d.first]=min(cnt[d.first],d.second);
}
for(auto x:adj[u])if(!used[x.first]){
for(auto d:v[x.first])if(d.first<=k)cnt[d.first]=inf;
v[x.first].clear();
}
for(auto x:adj[u])if(!used[x.first])decom(x.first);
}
int best_path(int N, int K, int H[][2], int L[])
{
n=N,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]});
}
for(int i=0;i<=K;i++)cnt[i]=inf;
cnt[0]=0;
decom(1);
return ans==inf?-1:ans;
}
