#include <bits/stdc++.h>
#include "race.h"
#define ll long long
#define ve vector
#define fi first
#define se second
using namespace std;
const int MAXN = 1e6+10;
typedef pair<ll, ll> pll;
ve<pll> g[MAXN];
int sz[MAXN];
bool del[MAXN];
ve<pll> comp;
ll k;
void updsz(int v, int p){
sz[v] = 1;
for(auto& to : g[v])
if(to.fi != p && !del[to.fi]){
updsz(to.fi, v);
sz[v] += sz[to.fi];
}
}
int centroid(int v, int p, int ssz){
for(auto& to : g[v])
if(to.fi != p && !del[to.fi] && 2*sz[to.fi] > ssz)
return centroid(to.fi, v, ssz);
return v;
}
struct vertex{
int sum, len, id;
};
void add(int v, int p, int len, int sum){
comp.push_back({sum, len});
for(auto& to : g[v])
if(to.fi != p && !del[to.fi])
add(to.fi, v, len + 1, to.se + sum);
}
int decomp(int v){
updsz(v, v);
int ssz = sz[v];
int res = 1e9;
v = centroid(v, v, ssz);
del[v] = 1;
map<ll, int> mp;
mp[0] = 0;
for(auto to : g[v]){
if(!del[to.fi]){
comp.clear();
add(to.fi, v, 1, to.se);
for(auto i : comp)
if(mp.find(k - i.fi) != mp.end())
res = min<int>(res, mp[k - i.fi] + i.se);
for(auto i : comp)
if(mp.find(i.fi) == mp.end() || mp[i.fi] > i.se)
mp[i.fi] = i.se;
}
}
for(auto to : g[v])
if(!del[to.fi])
res = min(res, decomp(to.fi));
return res;
}
int best_path(int N, int K, int H[][2], int L[])
{
k = K;
for(int i = 0; i < N - 1; i++){
int u = H[i][0], v = H[i][1], w = L[i];
g[u].push_back({v, w});
g[v].push_back({u, w});
}
int res = decomp(0);
if(res == 1e9)
return -1;
return res;
}
