#include <bits/stdc++.h>
#include "race.h"
#define ll long long
#define fi first
#define se second
#define sz(x) (int)x.size()
#define ALL(v) v.begin(),v.end()
#define MASK(k) (1LL << (k))
#define BIT(x, i) (((x) >> (i)) & 1)
#define oo (ll)1e18
#define INF (ll)1e9
#define MOD (ll)(1e9 + 19972207)
using namespace std;
template<class T1, class T2>
bool maximize(T1 &a, T2 b){if(a < b){a = b; return true;} return false;}
template<class T1, class T2>
bool minimize(T1 &a, T2 b){if(a > b){a = b; return true;} return false;}
template<class T1, class T2>
void add(T1 &a, T2 b){a += b; if(a >= MOD) a -= MOD;}
template<class T1, class T2>
void sub(T1 &a, T2 b){a -= b; if(a < 0) a += MOD;}
template<class T>
void cps(T &v){sort(ALL(v)); v.resize(unique(ALL(v)) - v.begin());}
const int MAX = 2e5 + 10, MAXVAL = 1e6 + 10;
int N, K;
vector<pair<int, int>> adj[MAX];
int nChild[MAX], ans = INF, dp[MAXVAL];
bool isDel[MAX];
void input(){
cin >> N >> K;
for(int i=1; i<N; i++){
int u, v, c;
cin >> u >> v >> c;
adj[u].push_back(make_pair(v, c));
adj[v].push_back(make_pair(u, c));
}
}
void countChild(int u, int p){
nChild[u] = 1;
for(auto o: adj[u]){
int v = o.fi;
if(v != p && !isDel[v]){
countChild(v, u);
nChild[u] += nChild[v];
}
}
}
int centroid(int u, int p, int n){
for(auto o: adj[u]){
int v = o.fi;
if(v != p && !isDel[v]){
if(nChild[v] * 2 > n) return centroid(v, u, n);
}
}
return u;
}
void dfs(int u, int p, int dist, int height, bool filling){
if(dist > K) return;
if(!filling){
minimize(ans, dp[K - dist] + height);
}
else{
minimize(dp[dist], height);
}
for(auto o: adj[u]){
int v = o.fi;
int newDist = dist + o.se;
if(v != p && !isDel[v])
dfs(v, u, newDist, height + 1, filling);
}
}
void reset(int u, int p, int dist){
if(dist > K) return;
dp[dist] = INF;
for(auto o: adj[u]){
int v = o.fi;
int newDist = dist + o.se;
if(v != p && !isDel[v])
reset(v, u, newDist);
}
}
void calc(int ver){
countChild(ver, 0);
int u = centroid(ver, 0, nChild[ver]);
dp[0] = 0;
for(auto o: adj[u]){
int v = o.fi;
int dist = o.se;
if(!isDel[v]){
dfs(v, u, dist, 1, 0);
dfs(v, u, dist, 1, 1);
}
}
reset(u, 0, 0);
isDel[u] = true;
for(auto o: adj[u]){
int v = o.fi;
if(!isDel[v]) calc(v);
}
}
int best_path(int n, int k, int H[][2], int L[]){
N = n;
K = k;
for(int i=0; i+1<N; i++){
int u = H[i][0];
int v = H[i][1];
int c = L[i];
adj[u].push_back(make_pair(v, c));
adj[v].push_back(make_pair(u, c));
}
memset(dp, 0x3f, sizeof dp);
calc(0);
return (ans >= INF ? -1 : ans);
}
// void solve(){
// }
// int main(){
// ios_base::sync_with_stdio(0); cin.tie(0);
// // freopen("mmgraph.inp", "r", stdin);
// // freopen("mmgraph.out", "w", stdout);
// int t = 1;
// // cin >> t;
// while(t--){
// input();
// solve();
// }
// return 0;
// }
