#include "race.h"
#include<bits/stdc++.h>
using namespace std;
#define pb push_back
#define ff first
#define ss second
#define in insert
const int mxn=2e5+10,mxk=1e6+10;
vector<pair<int,int> > g[mxn];
int global_answer=-1,n,k,vis[mxn],sub[mxn],nxt,mx;
int book_keeping,minimum_paths[mxk],achievable[mxk];
void dfs(int to,int fr)
{
sub[to]=1;
for(auto &x : g[to])
{
if(x.ff==fr || vis[x.ff]) continue;
dfs(x.ff,to);
sub[to]+=sub[x.ff];
}
}
void get_cen(int to,int fr,int sz)
{
int lomx=sz-sub[to];
for(auto &x : g[to])
{
if(x.ff==fr || vis[x.ff]) continue;
get_cen(x.ff,to,sz);
lomx=max(lomx,sub[x.ff]);
}
if(lomx<mx)
{
mx=lomx;
nxt=to;
}
}
void dfs2(int to,int fr,int current_cost,int current_length,int fill)
{
if(current_cost>k) return;
if (!fill)
{
if (achievable[k - current_cost] == book_keeping)
if (current_length + minimum_paths[k - current_cost] < global_answer || global_answer == -1)
global_answer = current_length + minimum_paths[k - current_cost];
if (current_cost == k)
if (current_length < global_answer || global_answer == -1)
global_answer = current_length;
}
else
{
if (achievable[current_cost] < book_keeping)
{
achievable[current_cost] = book_keeping;
minimum_paths[current_cost] = current_length;
}
else if (current_length < minimum_paths[current_cost])
{
achievable[current_cost] = book_keeping;
minimum_paths[current_cost] = current_length;
}
}
for(auto &x : g[to])
{
if(x.ff==fr || vis[x.ff]) continue;
dfs2(x.ff,to,current_cost+x.ss,current_length+1,fill);
}
}
void solve(int id)
{
dfs(id,-1);
if(sub[id]<=1) return;
mx=sub[id];
get_cen(id,-1,sub[id]);
id=nxt;
book_keeping++;
for(auto &x : g[id])
{
if(vis[x.ff]) continue;
dfs2(x.ff,id,x.ss,1,0);
dfs2(x.ff,id,x.ss,1,1);
}
vis[id]=1;
for(auto &x : g[id])
{
if(vis[x.ff]) continue;
solve(x.ff);
}
}
int best_path(int N, int K, int h[][2], int l[])
{
n=N;
k=K;
memset(vis,0,sizeof(vis));
for(int i=0; i<N-1; i++)
{
g[h[i][0]].pb({h[i][1],l[i]});
g[h[i][1]].pb({h[i][0],l[i]});
}
solve(0);
return global_answer;
}
