#include <bits/stdc++.h>
//#include "race.h"
#define task "road"
#define ll long long
#define fi first
#define se second
#define pii pair<ll, ll>
using namespace std;
const int N = 2e5 + 5;
ll n, k, ans = 1e9;
vector<pii> vt[N];
ll in[N], out[N], pos[N], sz[N], up[N][22];
pair<ll, int> h[N];
int cnt = 0;
void dfs(int u, int p)
{
in[u] = ++cnt;
pos[cnt] = u;
sz[u] = 1;
for(auto v : vt[u])
{
if(v.fi == p)
continue;
h[v.fi].fi = h[u].fi + v.se;
h[v.fi].se = h[u].se + 1;
up[v.fi][0] = u;
for(int i = 1; i <= 20; i++)
up[v.fi][i] = up[up[v.fi][i - 1]][i - 1];
dfs(v.fi, u);
sz[u] += sz[v.fi];
}
out[u] = cnt;
}
int lca(int u, int v)
{
if(h[u].se != h[v].se)
{
if(h[u].se < h[v].se)
swap(u, v);
int tmp = h[u].se - h[v].se;
for(int i = 0; i <= 20; i++)
if((tmp >> i) & 1)
u = up[u][i];
}
if(u == v)
return u;
for(int i = 20; i >= 0; i--)
if(up[u][i] != up[v][i])
{
u = up[u][i];
v = up[v][i];
}
return up[u][0];
}
map<ll, pii> mp;
void add(int u)
{
for(int i = in[u]; i <= out[u]; i++)
{
pii tmp = mp[h[pos[i]].fi];
if(tmp.fi == 0 || tmp.fi > h[pos[i]].se)
mp[h[pos[i]].fi] = {h[pos[i]].se, pos[i]};
}
}
void del(int u)
{
for(int i = in[u]; i <= out[u]; i++)
mp[h[pos[i]].fi] = {0, 0};
}
void solve(int u, int p)
{
pair<int, int> big = {0, -1};
for(auto v : vt[u])
if(v.fi != p)
big = max(big, {sz[v.fi], v.fi});
for(auto v : vt[u])
{
if(v.fi == big.se || v.fi == p)
continue;
solve(v.fi, u);
del(v.fi);
}
if(big.se != -1)
solve(big.se, u);
for(auto v : vt[u])
if(v.fi != big.se && v.fi != p)
add(v.fi);
mp[h[u].fi] = {h[u].se, u};
for(auto j : vt[u])
{
if(j.fi != big.se && j.fi != p)
for(int i = in[j.fi]; i <= out[j.fi]; i++)
{
int v = pos[i];
ll tmp = h[u].fi + k - (h[v].fi - h[u].fi);
pii huhu = mp[tmp];
if(huhu.fi == 0)
continue;
int haha = huhu.se;
if(lca(haha, v) == u)
ans = min(ans, huhu.fi - h[u].se + h[v].se - h[u].se);
// if(ans == 4)
// cout << u << " " << v << " " << haha << '\n';
}
}
pii huhu = mp[h[u].fi + k];
if(huhu.fi == 0)
return;
ans = min(ans, huhu.fi - h[u].se);
return;
}
int best_path(int m, int g, int h[][2], int l[])
{
n = m;
k = g;
for(int i = 0; i < n - 1; i++)
{
vt[h[i][0]].push_back({h[i][1], l[i]});
vt[h[i][1]].push_back({h[i][0], l[i]});
}
dfs(0, -1);
solve(0, -1);
if(ans == (int) 1e9)
return -1;
return ans;
}
//int main()
//{
// freopen(task".inp", "r", stdin);
// freopen(task".out", "w", stdout);
// ios_base::sync_with_stdio(false);
// cin.tie(NULL), cout.tie(NULL);
// cin >> n >> k;
// for(int i = 1; i < n; i++)
// {
// int x, y, w;
// cin >> x >> y >> w;
// vt[x].push_back({y, w});
// vt[y].push_back({x, w});
// }
// dfs(0, -1);
// cout << best_path();
// return 0;
//}
/*
4 3
0 1 1
1 2 2
1 3 4
11 12
0 1 3
0 2 4
2 3 5
3 4 4
4 5 6
0 6 3
6 7 2
6 8 5
8 9 6
8 10 7
*/
