#include<bits/stdc++.h>
#include "race.h"
#define mk make_pair
#define pb push_back
#define pii pair<int,int>
#define ll long long
#define f first
#define s second
using namespace std ;
const int inf = 1e9 + 5 ;
const int maxn = 2e5 + 5 ;
const int MAX = 1e6 + 5 ;
int ans = inf ;
int freq[MAX], k, sz[maxn], mark[maxn] ;
vector<pii> grafo[maxn] ;
// sz da subtree
// centroid p cada "nova arvore"
void dfs(int v, int p){
sz[v] = 1 ;
for(pii a : grafo[v]){
if(mark[a.f] || a.f == p) continue ;
dfs(a.f, v) ;
sz[v] += sz[a.f] ;
}
}
int centroid(int u, int p, int qtd){
for(pii a : grafo[u]){
if(a.f == p || mark[a.f] || sz[a.f]*2 <= qtd) continue ;
return centroid(a.f, u, qtd) ;
}
return u ;
}
void add(int u, int p, int v, int dist, int len){
if(dist > k) return ;
if(v == -1) freq[dist] = inf ;
else freq[dist] = min(freq[dist], len) ;
for(pii a : grafo[u]){
if(a.f == p || mark[a.f]) continue ;
add(a.f, u, v, dist + a.s, len + 1) ;
}
}
void solve(int u, int p, int dist, int len){
if(dist > k) return ;
ans = min(ans, freq[k-dist] + len) ;
for(pii a : grafo[u]){
if(a.f == p || mark[a.f]) continue ;
solve(a.f, u, dist + a.s, len+1) ;
}
}
void make_a(int v, int p){
dfs(v, p) ;
int c = centroid(v, p, sz[v]) ;
mark[c] = 1 ;
freq[0] = 0 ;
for(pii a : grafo[c]){
if(mark[a.f] || a.f == p) continue ;
solve(a.f, c, a.s, 1) ;
add(a.f, c, 1, a.s, 1) ;
}
// for(int i = 0 ; i <= k ; i++) cout << freq[i] << " " ;
// cout << "\n" ;
for(pii a : grafo[c]){
if(mark[a.f] || a.f == p) continue ;
add(a.f, c, -1, a.s, 1) ;
}
for(pii a : grafo[c]) if(!(a.f == p || mark[a.f])) make_a(a.f, c) ;
}
int best_path(int N, int K, int H[maxn][2], int L[maxn]){
for(int i = 0 ; i < N - 1 ; i++){
grafo[H[i][0]].pb(mk(H[i][1], L[i])) ;
grafo[H[i][1]].pb(mk(H[i][0], L[i])) ;
}
k = K ;
for(int i = 1 ; i <= k ; i++) freq[i] = inf ;
make_a(0, -1) ;
return (ans == inf ? -1 : ans) ;
}
/*int main(){
int mat[10][2] = {0, 1, 0, 2, 2, 3, 3, 4, 4, 5, 0, 6, 6, 7, 6, 8, 8, 9, 8, 10}, mat2[10] = {3, 4, 5, 4, 6, 3, 2, 5, 6, 7};
cout << best_path(11, 12, mat, mat2) << endl;
return 0;
}*/
