#include "race.h"
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
#include <bits/stdc++.h>
#define fi first
#define se second
#define pb push_back
#define sz(a) (int)a.size()
#define all(a) a.begin(), a.end()
#define rall(a) a.rbegin(), a.rend()
#define ff(i,a,b) for(int i=a;i<=b;i++)
#define fb(i,b,a) for(int i=b;i>=a;i--)
using namespace std;
using namespace __gnu_pbds;
typedef long long ll;
typedef pair<int,ll> pii;
const int maxn = 200005;
const int inf = 1e9 + 5;
template<typename T>
using ordered_set = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;
// os.order_of_key(k) the number of elements in the os less than k
// *os.find_by_order(k) print the k-th smallest number in os(0-based)
int n;
ll k;
vector<pii> g[maxn];
ll rez = inf;
map<ll,ll> dt[maxn];
void dfs(int v, int p, int duz, ll pw){
dt[v][pw] = duz;
// cout << "v: " << v << endl;
// cout << "duz: " << duz << endl;
// cout << "pw: " << pw << endl;
// cout << endl;
for(auto c : g[v]){
int u = c.fi;
ll w = c.se;
if(u != p){
dfs(u, v, duz + 1, pw + w);
int x = v, y = u;
if(sz(dt[x]) < sz(dt[y]))swap(dt[x], dt[y]);
for(auto c : dt[y]){
if(dt[x].count(k - c.fi + 2 * pw))rez = min(rez, dt[x][k - c.fi + 2 * pw] + c.se - 2 * duz);
if(dt[x][c.fi] == 0)dt[x][c.fi] = c.se;
else dt[x][c.fi] = min(dt[x][c.fi], c.se);
}
}
}
// cout << "v: " << v << endl;
// for(auto c : dt[v])cout << c.fi << " " << c.se << endl;
// cout << "-----------------------------" << endl;
}
int best_path(int N, int K, int H[][2], int L[]){
n = N;
k = K;
ff(i,1,n){
g[i].clear();
dt[i].clear();
}
ff(i,0,n - 2){
int u = H[i][0] + 1;
int v = H[i][1] + 1;
ll w = L[i];
g[u].pb({v, w});
g[v].pb({u, w});
}
dfs(1, -1, 1, 0);
return (rez == inf ? -1 : rez);
}
//int main()
//{
// ios::sync_with_stdio(false);
// cout.tie(nullptr);
// cin.tie(nullptr);
// cin >> n >> k;
// ff(i,1,n - 1){
// int u, v, w;
// cin >> u >> v >> w;
// g[u].pb({v, w});
// g[v].pb({u, w});
// }
// dfs(1, -1, 1, 0);
// cout << rez << endl;
// return 0;
//}
/**
11 12
1 2 3
1 3 4
3 4 5
4 5 4
5 6 6
1 7 3
7 8 2
7 9 5
9 10 6
9 11 7
// probati bojenje sahovski ili slicno
**/
