#include "highway.h"
#include "bits/stdc++.h"
using namespace std;
using ll = long long;
#define sz(a) (int)a.size()
#define all(a) a.begin(),a.end()
#define rall(a) a.rbegin(),a.rend()
void dfs(int u, int par, vector<vector<int>>& adj, vector<int>& p, vector<int>& depth) {
p[u] = par;
for(int v: adj[u]) {
if(v == par) continue;
depth[v] = depth[u] + 1;
dfs(v, u, adj, p, depth);
}
}
void bfsTree(int start, vector<vector<int>>& adj, vector<vector<int>>& g, vector<bool>& use) {
queue<int> q; q.push(start);
vector<bool> vis(sz(g), 0);
vis[start] = 1;
while(!q.empty()) {
int u = q.front();
assert(use[u] == true);
q.pop();
for(int v: g[u]) {
if(!vis[v] && use[v]) {
adj[u].push_back(v);
adj[v].push_back(u);
vis[v] = true;
q.push(v);
}
}
}
}
ll init;
ll paiu;
map<vector<int>, ll> mp;
ll query(vector<int>& c) {
if(!mp.count(c)) mp[c] = ask(c);
return mp[c];
}
int find(int start, int n, vector<int>& u, vector<int>& v, vector<bool>& use) {
map<pair<int, int>, int> idx;
vector<vector<int>> adj(n), g(n);
vector<int> p(n, 0), depth(n, 0);
int m = u.size();
for(int i = 0; i < m; ++i) {
g[u[i]].push_back(v[i]);
g[v[i]].push_back(u[i]);
idx[{u[i], v[i]}] = idx[{v[i], u[i]}] = i;
}
bfsTree(start, adj, g, use);
dfs(start, -1, adj, p, depth);
vector<int> c(m, 1);
for(int i = 0; i < n; ++i) {
if(p[i] != -1 && use[i]) c[idx[{i, p[i]}]] = 0;
}
init = query(c);
vector<pair<int, int>> bruh;
for(int i = 0; i < n; ++i) {
if(p[i] != -1 && use[i])
bruh.push_back({depth[i], i});
}
sort(rall(bruh));
vector<int> nodes;
for(int i = 0; i < sz(bruh); ++i) {
nodes.push_back(bruh[i].second);
}
if(sz(nodes) == 0) {
return start;
}
assert(sz(nodes) > 0);
vector<int> rem = c;
vector<int> ids(n, -1);
for(int i = 0; i < sz(nodes); ++i) {
ids[i] = idx[{nodes[i], p[nodes[i]]}];
}
int l = 0, r = sz(nodes) - 1, pp = -1;
while(l <= r) {
int mid = (l + r) >> 1;
for(int i = 0; i <= mid; ++i) {
if(p[nodes[i]] == -1) continue;
c[ids[i]] = 1;
}
if(query(c) > init) {
pp = mid;
r = mid - 1;
} else l = mid + 1;
c = rem;
}
if(pp == -1) return start;
return nodes[pp];
}
void get_distances(int s, vector<vector<int>>& adj, vector<int>& d) {
d.assign((int)adj.size(), INT_MAX);
d[s] = 0;
queue<int> q;
q.push(s);
while(!q.empty()) {
int u = q.front();
q.pop();
for(int v: adj[u]) {
if(d[v] == INT_MAX) {
d[v] = d[u] + 1;
q.push(v);
}
}
}
}
void find_pair(int n, vector<int> u, vector<int> v, int a, int b) {
vector<int> noo(sz(u), 0);
init = query(noo);
paiu = init;
vector<vector<int>> adj(n);
for(int i = 0; i < (int)u.size(); ++i) adj[u[i]].push_back(v[i]), adj[v[i]].push_back(u[i]);
int pos = -1, l = 0, r = sz(u) - 1;
while(l <= r) {
int mid = (l + r) >> 1;
for(int i = 0; i <= mid; ++i) noo[i] = 1;
if(query(noo) > init) {
pos = mid;
r = mid - 1;
} else l = mid + 1;
for(int i = 0; i <= mid; ++i) noo[i] = 0;
}
vector<int> du(n), dv(n);
get_distances(u[pos], adj, du);
get_distances(v[pos], adj, dv);
vector<bool> use(n, false);
for(int i = 0; i < n; ++i) {
if(du[i] < dv[i]) use[i] = true;
}
int s = find(u[pos], n, u, v, use);
use.assign(n, false);
for(int i = 0; i < n; ++i) {
if(dv[i] < du[i]) use[i] = true;
}
int t = find(v[pos], n, u, v, use);
answer(t, s);
}
