#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp> // Common file
#include <ext/pb_ds/tree_policy.hpp> // Including tree_order_statistics_node_update
#include <ext/pb_ds/detail/standard_policies.hpp>
#define xc3(x) (x*(x-1)*(x-2)/6)
#define xc2(x) ((x)*((x)-1)/2)
#define abs(x) ((x)>0?(x):-((x)))
#define min(x,y) ((x)>(y)?(y):(x))
//#define debug 1
using namespace std;
using namespace __gnu_pbds;
//void FILEREAD(){freopen("text_input.txt","r",stdin);freopen("output.txt","w",stdout);}
#define ll long long
#define ull unsigned long long
#define pi pair<int,int>
#define pll pair<long long,long long>
#define pli pair<long long,int>
#define pil pair<int,long long>
#define vi vector<int>
#define vll vector<long long>
#define vpi vector<pair<int,int>>
#define vpll vector<pair<long long,long long>>
#define vvi vector<vector<int>>
#define vvll vector<vector<long long>>
#define vvpi vector<vector<pair<int,int>>>
#define vvpll vector<vector<pair<long,long>>>
#define vec vector
#define pr pair
#define fi first
#define se second
#define fr(i,j) for(int i=0;i<j;i++)
#define testcase(x) int x;cin>>x;while(x--)solve()
#define vecinp(v) for(auto &in_vx:v)cin>>in_vx
#define pb push_back
typedef tree<ll,null_type,less<int>,rb_tree_tag,tree_order_statistics_node_update> ordered_Set;
ordered_Set os;
#define MAX 99999997
#define MOD 92182
#define maxM 200002
vvpi adj(maxM,vpi(0));
vec<bool> visited(maxM);
vi prec(maxM);
ll ans = LLONG_MAX;
int NN,KK;
void edge(int v1,int v2,int val){
adj[v1].pb({v2,val});
adj[v2].pb({v1,val});
}
int precf(int n,int p){
prec[n] = 1;
for(auto &x:adj[n]){
if(x.first!=p && !visited[x.first])prec[n] += precf(x.first,n);
}
return prec[n];
}
int centroid(int n,int p,int u){
for(auto &x:adj[n]){
if(x.first!=p && !visited[x.first] && 2*prec[x.first]>u)return centroid(x.first,n,u);
}
return n;
}
int d = 0;
vi cnt(maxM,MAX);
void dfs(int type, int node , int parent , int complexity , int km){
if(km>KK)return;
d = max(d,complexity);
if(type) ans = min(ans,cnt[KK-km]+complexity);
else cnt[km] = min(cnt[km],complexity);
for(auto &x:adj[node]){
if(x.first == parent || visited[x.first])continue;
dfs(type,x.first,node,complexity+1,km+x.second);
}
}
void solve(int n){
int cen = centroid(n,-1,precf(n,-1));
visited[cen] = 1;
cnt[0]=1;
// MAIN OPERATIONS
d = 0;
for(auto &x:adj[cen]){
if(visited[x.first])continue;
dfs(1,x.first,cen,1,x.second);
dfs(0,x.first,cen,1,x.second);
}
fill(cnt.begin(),cnt.begin()+d,MAX);
// GO TO MY CHILDREN AND REPEAT
for(auto &x:adj[cen]){
if(visited[x.first])continue;
solve(x.first);
}
}
int best_path(int N,int K,int H[][2], int L[]){
// OUTPUT && REMOVE LATER
fr(i,N-1){
edge(H[i][0],H[i][1],L[i]);
}
NN = N;
KK = K;
// MAIN CODE STARTS HERE
//
solve(0);
return (ans>MAX-1000?-1:ans);
}
