#include <bits/stdc++.h>
#include "race.h"
using namespace std;
typedef long long ll;
typedef pair<int, int> pii;
template<class T> bool ckmin(T& a, const T& b) { return b < a ? a = b, 1 : 0; }
template<class T> bool ckmax(T& a, const T& b) { return a < b ? a = b, 1 : 0; }
#define sz(x) (int)x.size()
const int MAXN = 2e5+5, INF = 1e9;
int n, k, ans = INF, h[MAXN][2], l[MAXN];
vector<pii> arr[MAXN];
set<pii> vals[MAXN];
pii offset[MAXN];
void solve(int at, int parent, int cost){
// Find the largest subtree
int big = at, bigCost = 0;
for (pii i : arr[at]){
if (i.first != parent){
solve(i.first, at, i.second);
if (vals[i.first].size() > vals[big].size()){
big = i.first;
bigCost = i.second;
}
}
}
if (at != big){
swap(vals[at], vals[big]); // Copy the largest subtree
offset[at] = offset[big];
offset[at].first += bigCost;
offset[at].second++;
}
// Manually add the remaining elements
for (pii i : arr[at]){
if (i.first != parent && i.first != big){ // Since vals[big] is empty now (we called swap() on it), we don't have to worry about it anymore
for (pii x : vals[i.first]){
int costNeeded = k - (x.first + offset[i.first].first + i.second) - offset[at].first;
int adjDist = x.second + offset[i.first].second - offset[at].second;
if (costNeeded == 0){
ckmin(ans, adjDist + offset[at].second);
continue;
}
auto it = vals[big].lower_bound({costNeeded, -INF});
if (it != vals[big].end() && (*it).first == costNeeded){
ckmin(ans, (*it).second + offset[at].second + adjDist);
}
}
for (pii x : vals[i.first]){
int adjCost = (x.first + offset[i.first].first + i.second) - offset[at].first;
int adjDist = x.second + offset[i.first].second - offset[at].second;
vals[at].insert({adjCost, adjDist});
}
}
}
auto it = vals[at].lower_bound({k - offset[at].first, -INF});
if (it != vals[big].end() && (*it).first == k - offset[at].first){
ckmin(ans, (*it).second + offset[at].second);
}
vals[at].insert({-offset[at].first, -offset[at].second});
}
int best_path(int N, int K, int h[][2], int l[]){
n = N, k = K;
for (int i=0; i<n-1; i++){
int a = h[i][0], b = h[i][1];
arr[a].push_back({b, l[i]});
arr[b].push_back({a, l[i]});
}
solve(0, -1, 0);
return ans != INF ? ans : -1;
}
/**
* Debugging checklist:
* - Reset everything after each TC
* - Integer overflow, index overflow
* - Special cases?
*/
