#include "race.h"
#include <bits/stdc++.h>
using namespace std;
const int nx=2e5+5, kx=1e6+5;
int n, k, sz[nx], ans=INT_MAX, dp[kx];
bool used[nx];
vector<pair<int, int>> d[nx], res[nx];
int dfssz(int u, int p)
{
sz[u]=1;
for (auto [v, w]:d[u]) if (v!=p&&!used[v]) sz[u]+=dfssz(v, u);
return sz[u];
}
int findcentroid(int u, int p, int rtsz)
{
for (auto [v, w]:d[u]) if (v!=p&&!used[v]&&2*sz[v]>rtsz) return findcentroid(v, u, rtsz);
return u;
}
void dfs(int u, vector<pair<int, int>> &vec, int ds, int len, int p)
{
if (ds>k) return;
vec.push_back({ds, len});
for (auto [v, w]:d[u]) if (v!=p&&!used[v]) dfs(v, vec, ds+w, len+1, u);
}
void decom(int u)
{
u=findcentroid(u, -1, dfssz(u, -1));
used[u]=1;
for (auto [v, w]:d[u])
{
if (used[v]) continue;
dfs(v, res[v], w, 1, u);
for (auto [ds, len]:res[v]) ans=min(ans, len+dp[k-ds]);
for (auto [ds, len]:res[v]) dp[ds]=min(dp[ds], len);
}
for (auto [v, w]:d[u])
{
if (used[v]) continue;
for (auto [ds, len]:res[v]) dp[ds]=1e9;
res[v].clear();
}
for (auto [v, w]:d[u]) if (!used[v]) decom(v);
}
int best_path(int N, int K, int H[][2], int L[])
{
n=N; k=K;
dp[0]=0;
for (int i=1; i<=k; i++) dp[i]=1e9;
for (int i=0; i<n-1; i++) d[H[i][0]].push_back({H[i][1], L[i]}), d[H[i][1]].push_back({H[i][0], L[i]});
decom(0);
return ans>=1e9?-1:ans;
}
