#include "race.h"
#include <bits/stdc++.h>
using namespace std;
using ll = long long;
const int N = 2e5+10;
const int MAX = 1e6+10;
int n, k;
vector< pair<int,int> > g[200010];
int sub[N];
bool Deleted[N];
void dfs(int u, int f) {
sub[u] = 1;
for(auto it : g[u]) if(it.first != f && !Deleted[it.first]) {
dfs(it.first, u);
sub[u] += sub[it.first];
}
}
int get_centroid(int u, int f, int lim) {
int ret = -1;
for(auto it : g[u]) if(it.first != f && !Deleted[it.first]) {
if(sub[it.first] * 2 > lim) {
ret = get_centroid(it.first, u, lim);
break;
}
} if(ret == -1) return u;
return ret;
}
int F[MAX];
int get_subtree(int u, int f, ll cost, int cnt) {
int ret = N + N;
if(cost <= k) ret = F[k - cost] + cnt;
if(cost == k) ret = min(ret, cnt);
for(auto it : g[u]) if(it.first != f && !Deleted[it.first])
ret = min(ret, get_subtree(it.first, u, cost + it.second, cnt + 1));
return ret;
}
void upd_subtree(int u, int f, ll cost, int cnt) {
if(cost < MAX) F[cost] = min(F[cost], cnt);
for(auto it : g[u]) if(it.first != f && !Deleted[it.first])
upd_subtree(it.first, u, cost + it.second, cnt + 1);
}
int calc(int u) {
for(int i = 0; i <= k; i++) F[i] = N+N;
int ans = N + N;
for(auto it : g[u]) if(!Deleted[it.first]) {
ans = min(ans, get_subtree(it.first, u, it.second, 1));
upd_subtree(it.first, u, it.second, 1);
} return ans;
}
int solve(int s) {
dfs(s,-1);
int u = get_centroid(s, -1, sub[s]);
int ret = calc(u);
Deleted[u] = true;
for(auto it : g[u]) if(!Deleted[it.first])
ret = min(ret, solve(it.first));
return ret;
}
int best_path(int N_, int K, int H[][2], int L[]) {
n = N_; k = K;
for(int i = 0; i < n-1; i++) {
g[H[i][0]].push_back({H[i][1], L[i]});
g[H[i][1]].push_back({H[i][0], L[i]});
}
int ans = solve(0);
if(ans >= N+N) return -1;
return ans;
}
