#include "race.h"
#include <bits/stdc++.h>
#define rep(i,x,n) for(int i=x; i<n; i++)
using namespace std;
constexpr int INF=1e9;
int best_path(int N, int K, int H[][2], int L[]) {
int m=INF;
vector<bool> V(N);
vector<int> C(N, 1), D(K+1, INF), X;
vector<pair<int, int>> Y;
vector<vector<pair<int, int>>> G(N);
rep(i, 0, N-1) {
int x=H[i][0], y=H[i][1], z=L[i];
G[x].push_back({y, z});
G[y].push_back({x, z});
}
#define ITER(i) for(auto[j,w]:G[i]) if(j!=p && !V[j])
function<void(int, int)> cnt=[&](int i, int p) {
ITER(i) cnt(j, i), C[i]+=C[j];
};
function<int(int, int, int)> cent=[&](int i, int p, int n) {
ITER(i) if(C[j]>n/2) {
C[j]+=C[i]-=C[j];
return cent(j, i, n);
}
return i;
};
function<void(int, int, int, int)> f=[&](int i, int p, int d, int k) {
X.push_back(d);
m=min(m, k+D[K-d]);
ITER(i) if(d+w<=K && k+1<m) {
f(j, i, d+w, k+1);
if(i==p) {
for(auto[x,y]:Y) D[x]=min(D[x], y);
Y.clear();
}
}
Y.push_back({d, k});
};
function<void(int, int)> cd=[&](int i, int p) {
V[i=cent(i, p, C[i])]=true, D[0]=0;
f(i, i, 0, 0);
for(int x:X) D[x]=INF;
X.clear();
ITER(i) cd(j, i);
};
cnt(0, 0);
cd(0, 0);
return (m==INF?-1:m);
}
