//#include "race.h"
#include <bits/stdc++.h>
#define pii pair<int, int>
#define x first
#define y second
using namespace std;
const int N = 2e5 + 5;
const int M = 1e6 + 5;
int n, k, book;
int ans = -1;
int sub[N], dp[M], tim[M];
vector<pii> g[N];
bitset<N> chk;
int cent, mxnode;
int calcsz(int u, int p) {
sub[u] = 1;
for(pii v : g[u]) if(v.x != p && !chk[v.x]) sub[u] += calcsz(v.x, u);
return sub[u];
}
void centroid(int u, int p, int all) {
int mxsub = all - sub[u];
for(pii v : g[u]) if(v.x != p && !chk[v.x]) {
centroid(v.x, u, all);
mxsub = max(mxsub, sub[v.x]);
}
if(mxsub < mxnode) cent = u, mxnode = mxsub;
}
void dfs(int u, int p, int len, int cnt) {
if(len > k) return;
if(tim[k - len] == book && (ans == -1 || cnt + dp[k - len] < ans)) ans = cnt + dp[k - len];
if(len == k && (ans == -1 || cnt < ans)) ans = cnt;
for(pii v : g[u]) if(v.x != p && !chk[v.x]) dfs(v.x, u, len + v.y, cnt + 1);
}
void prep(int u, int p, int len, int cnt) {
if(len > k) return;
if(tim[len] < book || cnt < dp[len]) tim[len] = book, dp[len] = cnt;
for(pii v : g[u]) if(v.x != p && !chk[v.x]) dfs(v.x, u, len + v.y, cnt + 1);
}
void dfs2(int u, int p, int cost, int edge, bool fill) {
if(cost > k) return;
if(!fill) {
if(tim[k - cost] == book && (edge + dp[k - cost] < ans || ans == -1)) ans = edge + dp[k - cost];
if(cost == k && (edge < ans || ans == -1)) ans = edge;
} else if(tim[cost] < book || edge < dp[cost]) tim[cost] = book, dp[cost] = edge;
for(pii v : g[u]) if(!chk[v.x] && v.x != p) {
dfs2(v.x, u, cost + v.y, edge + 1, fill);
}
}
void proc(int u) {
book++;
if(calcsz(u, u) <= 1) return;
mxnode = sub[u] + 1;
centroid(u, u, sub[u]);
u = cent;
//printf("%d\n", u);
for(pii v : g[u]) if(!chk[v.x]) {
dfs2(v.x, u, v.y, 1, false);
dfs2(v.x, u, v.y, 1, true);
}
chk[u] = 1;
for(pii v : g[u]) if(!chk[v.x]) proc(v.x);
}
int best_path(int N, int K, int H[][2], int L[])
{
n = N, k = K;
for(int i = 0; i < n - 1; i++) {
g[H[i][0]].emplace_back(H[i][1], L[i]);
g[H[i][1]].emplace_back(H[i][0], L[i]);
}
proc(0);
return ans;
}
/*int main() {
int n, k, h[100][2], l[100];
scanf("%d%d", &n, &k);
for(int i = 0; i < n - 1; i++) {
scanf("%d %d %d", &h[i][0], &h[i][1], &l[i]);
}
printf("%d", best_path(n, k, h, l));
return 0;
}*/
