#include "race.h"
#include <vector>
#include <queue>
#include <algorithm>
using namespace std;
// frozen
int i,n,k;
int answer = 999999999;
vector<pair<int,int> > edge[200002];
queue<pair<int,int> > q;
int root[1000002],small[1000002];
bool check[200002];
int find_middle(int x){
return x;
}
void dfs(int v,long long sum,int cnt){
int i,sizes;
int nextv,cost;
if(sum > k) return;
check[v] = true;
q.push(make_pair(sum,cnt));
sizes = edge[v].size();
for(i=0; i<sizes; i++){
nextv = edge[v][i].first;
cost = edge[v][i].second;
if(check[nextv]) continue;
dfs(nextv,sum+cost,cnt+1);
}
check[v] = false;
}
void race(int x){
int i,sizes;
int nextv;
int tsum,tcnt;
int v = find_middle(x);
check[v] = true;
sizes = edge[v].size();
root[0] = v;
small[0] = 0;
for(i=0; i<sizes; i++){
nextv = edge[v][i].first;
if(check[nextv]) continue;
dfs(nextv,edge[v][i].second,1);
while(!q.empty()){
tsum = q.front().first;
tcnt = q.front().second;
q.pop();
if(root[k-tsum] == v && answer > small[k-tsum] + tcnt) answer = small[k-tsum] + tcnt;
}
dfs(nextv,edge[v][i].second,1);
while(!q.empty()){
tsum = q.front().first;
tcnt = q.front().second;
q.pop();
if(root[tsum] != v){
root[tsum] = v;
small[tsum] = tcnt;
}else if(small[tsum] > tcnt) small[tsum] = tcnt;
}
}
for(i=0; i<sizes; i++){
nextv = edge[v][i].first;
if(!check[nextv]) race(nextv);
}
}
int best_path(int N, int K, int H[][2], int L[])
{
int i;
n = N; k = K;
for(i=0; i<n-1; i++){
edge[H[i][0]].push_back(make_pair(H[i][1],L[i]));
edge[H[i][1]].push_back(make_pair(H[i][0],L[i]));
}
for(i=0; i<=k; i++) root[i] = -1;
race(0);
if(answer == 999999999) answer = -1;
return answer;
}
