#pragma GCC optimize("Ofast")
#include "race.h"
#include <bits/stdc++.h>
using namespace std;
int n, k;
vector<pair<int,int>> AdjList[200005];
bitset<200005> marked;
int sz[200005];
int getSz(int u, int p) {
sz[u] = 1;
for(auto v: AdjList[u]) {
if(v.first==p) continue;
if(marked[v.first]) continue;
sz[u] += getSz(v.first, u);
}
return sz[u];
}
int getCentroid(int u, int p, int compSz) {
if(sz[u]*2 < compSz)
return -1;
for(auto v: AdjList[u]) {
if(v.first==p) continue;
if(marked[v.first]) continue;
if(sz[v.first]*2 > compSz)
return getCentroid(v.first, u, compSz);
}
return u;
}
int dp[1000005];
int ans = 1<<29;
void checkSecondLeg(int u, int p, int d, int l) {
ans = min(ans, l + dp[k-d]);
for(auto v: AdjList[u]) {
if(v.first==p) continue;
if(marked[v.first]) continue;
if(d+v.second > k) continue;
checkSecondLeg(v.first, u, d+v.second, l+1);
}
}
void markFirstLeg(int u, int p, int d, int l) {
dp[d] = min(dp[d], l);
for(auto v: AdjList[u]) {
if(v.first==p) continue;
if(marked[v.first]) continue;
if(d+v.second > k) continue;
markFirstLeg(v.first, u, d+v.second, l+1);
}
}
void unmarkFirstLeg(int u, int p, int d, int l) {
dp[d] = 1<<29;
for(auto v: AdjList[u]) {
if(v.first==p) continue;
if(marked[v.first]) continue;
if(d+v.second > k) continue;
unmarkFirstLeg(v.first, u, d+v.second, l+1);
}
}
void doDecomp(int u) {
getSz(u, -1);
int centre = getCentroid(u, -1, sz[u]);
for(auto v: AdjList[centre]) {
if(marked[v.first])
continue;
if(v.second > k) continue;
checkSecondLeg(v.first, centre, v.second, 1);
markFirstLeg(v.first, centre, v.second, 1);
}
for(auto v: AdjList[centre]) {
if(marked[v.first])
continue;
if(v.second > k) continue;
unmarkFirstLeg(v.first, centre, v.second, 1);
}
dp[0] = 0;
marked[centre]=1;
for(auto v: AdjList[centre]) {
if(marked[v.first])
continue;
doDecomp(v.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++) {
AdjList[H[i][0]].push_back({H[i][1], L[i]});
AdjList[H[i][1]].push_back({H[i][0], L[i]});
}
ans = 1<<29;
for(int i = 1; i <= K; i++)
dp[i] = 1<<29;
dp[0] = 0;
doDecomp(0);
if(ans == 1<<29)
ans = -1;
return ans;
}
