#include "dreaming.h"
#include <bits/stdc++.h>
#define endl "\n"
#define F first
#define S second
#define pb push_back
typedef long long ll;
using namespace std;
const int N = 1e6+5;
const long long oo = 1e18 ;
vector <pair <ll,ll>> v[N] ;
ll n , m , ans , best , mx , dis[N] , len ;
bool vis[N] ;
void dfs (ll u , ll p , ll cost)
{
dis[u] = cost ;
vis[u] = true ;
for (auto it : v[u])
{
if (it.F != p)
dfs(it.F , u , cost + it.S);
}
}
bool dfs2 (ll u , ll p , ll cost , ll gol)
{
bool is = false ;
for (auto it : v[u])
{
if (it.F != p)
is |= dfs2(it.F , u , cost + it.S , gol) ;
}
is |= (u == gol);
if (is)
best = min (best , max(cost , len-cost));
return is ;
}
ll p1 , p2 ;
ll far (ll p)
{
mx = 0 ; ll ret ;
for (int i = 1 ; i<=n ; i++)
dis[i] = 0 ;
dfs(p , p , 0) ;
for (int i = 1 ; i<=n ; i++)
{
if (dis[i] >= mx)
ret = i , mx = dis[i] ;
}
return ret ;
}
ll get (ll p)
{
p1 = far(p);
p2 = far(p1);
len = mx ;
best = oo ;
dfs2(p1 , p1 , 0 , p2) ;
return best ;
}
int travelTime(int N, int M, int L, int A[], int B[], int T[])
{
n = N ; m = M ;
for (int i = 0 ; i<m ; i++)
{
v[B[i]].pb({A[i] , T[i]});
v[A[i]].pb({B[i] , T[i]});
}
ans += get(1) ;
ll bans = len ;
for (int i = 1 ; i<=n ; i++)
{
if (!vis[i])
{
ans += get(i) ;
break ;
}
}
bans = max(bans , len) ;
return max(bans , ans + L) ;
}
