//#pragma GCC target("avx2")
//#pragma GCC optimization("O3")
//#pragma GCC optimization("unroll-loops")
#include<bits/stdc++.h>
using namespace std;
#define ll long long
#define pii pair<int, int>
#define pll pair<ll, ll>
#define ff first
#define ss second
#define pb push_back
#define SZ(x) ((int)(x).size())
#define all(x) x.begin(), x.end()
#define rep(i, a, b) for(int i = (a); i < (b); i++)
#define Re(i, a, b) for(int i = (a); i >= (b); i--)
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
const int MAXN = 1e3;
vector<vector<int>> g;
int timer;
void dfs(int v, int p, vector<int>& labels){
int tin = timer++;
for(int u : g[v]){
if(u ^ p){
dfs(u, v, labels);
}
}
int tou = timer - 1;
labels[v] = MAXN * tin + tou;
}
vector<int> label(int N, int K, vector<int> u, vector<int> v){
g.resize(N);
rep(i, 0, N){
g[i].clear();
}
auto add_edge = [&](int a, int b){
g[a].pb(b);
g[b].pb(a);
};
rep(i, 0, N - 1){
add_edge(u[i], v[i]);
}
vector<int> labels(N);
timer = 0;
dfs(0, -1, labels);
return labels;
}
int find_next_station(int a, int b, vector<int> c){
auto get_label = [&](int x){
pii ans = {x / MAXN, x % MAXN};
return ans;
};
auto ancestor = [&] (pii u, pii v){
bool is = (u.ff <= v.ff && v.ss <= u.ss);
return is;
};
pii s = get_label(a), t = get_label(b);
for(int x : c){
pii u = get_label(x);
if(ancestor(s, u)){
if(ancestor(u, t))
return x;
} else{
if(ancestor(t, u))
return x;
}
}
}
