#include "race.h"
#include "bits/stdc++.h"
using namespace std;
vector < pair <int, int> > g[200010];
int ans;
int len;
void dfs(int x, int par, map <long long, int> &f, long long &add, int &extra) {
add = 0;
extra = 0;
f[0] = 0;
for(auto i : g[x]) {
if(i.first == par) continue;
map <long long, int> t;
long long plus;
int rem;
dfs(i.first, x, t, plus, rem);
plus += i.second;
rem += 1;
if(t.size() > f.size()) {
f.swap(t);
swap(add, plus);
swap(extra, rem);
}
for(auto i : t) {
if(f.find(len - i.first - plus - add) != f.end()) {
ans = min(ans, i.second + f[len - i.first - plus - add] + extra + rem);
}
}
plus -= add;
rem -= extra;
for(auto i : t) {
long long p = i.first + plus;
if(f.find(p) == f.end()) {
f[p] = i.second + rem;
} else {
f[p] = min(f[p], i.second + rem);
}
}
}
}
int best_path(int N, int K, int H[][2], int L[])
{
ans = INT_MAX;
len = K;
for(int i = 0; i <= N; i++) g[i].clear();
for(int i = 0; i < N-1; i++) {
int p = H[i][0];
int q = H[i][1];
int r = L[i];
g[p].push_back(make_pair(q, r));
g[q].push_back(make_pair(p, r));
}
map <long long, int> f;
long long add;
int extra;
dfs(0, -1, f, add, extra);
return ans == INT_MAX ? -1 : ans;
}
