#include <bits/stdc++.h>
#ifndef LOCAL
#include "race.h"
#endif
/*
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
*/
using namespace std;
// using namespace __gnu_pbds;
using namespace chrono;
// mt19937 rng((int) std::chrono::steady_clock::now().time_since_epoch().count());
/*
template <class T> using ordered_set = tree <T, null_type, less <T>, rb_tree_tag, tree_order_statistics_node_update>;
*/
//***************** CONSTANTS *****************
const int MXN = 100000;
//***************** GLOBAL VARIABLES *****************
vector<array<int, 2>> g[MXN];
map<int, int> mp[MXN];
int ans = INT_MAX, K;
//***************** AUXILIARY STRUCTS *****************
//***************** MAIN BODY *****************
void dfs(int p, int u){
mp[u][0] = 0;
for(auto& [v, d] : g[u]) if(v != p){
dfs(u, v);
if(mp[u].size() < mp[v].size())
swap(mp[u], mp[v]);
for(auto& [t, l] : mp[v]){
if(t + d > K) continue;
int T = t + d;
if(mp[u].find(K - T) != mp[u].end()) ans = min(ans, mp[u][K - T] + l + 1);
if(mp[u].find(T) != mp[u].end()) mp[u][T] = min(mp[u][T], l + 1);
else mp[u][T] = l + 1;
}
}
// cout << u << '\n';
// for(auto& [t, l] : mp[u])
// cout << t << ' ' << l << '\n';
// cout << "***\n";
}
int best_path(int N, int k, int H[][2], int L[]){
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]});
}
K = k;
dfs(0, 0);
return (ans == INT_MAX ? -1 : ans);
}
//***************** *****************
#ifdef LOCAL
int32_t main(){
ios_base::sync_with_stdio(NULL);
cin.tie(NULL);
#ifdef LOCAL
auto begin = high_resolution_clock::now();
#endif
int tc = 1;
// cin >> tc;
for (int t = 0; t < tc; t++){
int N, k;
cin >> N >> k;
int H[N-1][2], L[N-1];
for(int i = 0; i < N-1; i++)
cin >> H[i][0] >> H[i][1] >> L[i];
cout << best_path(N, k, H, L) << '\n';
}
#ifdef LOCAL
auto end = high_resolution_clock::now();
cout << fixed << setprecision(4);
cout << "Execution Time: " << duration_cast<duration<double>>(end - begin).count() << "seconds" << endl;
#endif
return 0;
}
#endif
/*
If code gives a WA, check for the following :
1. I/O format
2. Are you clearing all global variables in between tests if multitests are a thing
3. Can you definitively prove the logic
4. If the code gives an inexplicable TLE, and you are sure you have the best possible complexity,
use faster io
*/
