#include "highway.h"
#include <bits/stdc++.h>
#define MP make_pair
#define PB push_back
#define st first
#define nd second
#define rd third
#define FOR(i, a, b) for(int i =(a); i <=(b); ++i)
#define RE(i, n) FOR(i, 1, n)
#define FORD(i, a, b) for(int i = (a); i >= (b); --i)
#define REP(i, n) for(int i = 0;i <(n); ++i)
#define VAR(v, i) __typeof(i) v=(i)
#define FORE(i, c) for(VAR(i, (c).begin()); i != (c).end(); ++i)
#define ALL(x) (x).begin(), (x).end()
#define SZ(x) ((int)(x).size())
using namespace std;
template<typename TH> void _dbg(const char* sdbg, TH h) { cerr<<sdbg<<"="<<h<<"\n"; }
template<typename TH, typename... TA> void _dbg(const char* sdbg, TH h, TA... t) {
while(*sdbg != ','){cerr<<*sdbg++; }cerr<<"="<<h<<","; _dbg(sdbg+1, t...);
}
#ifdef LOCAL
#define debug(...) _dbg(#__VA_ARGS__, __VA_ARGS__)
#define debugv(x) {{cerr <<#x <<" = "; FORE(itt, (x)) cerr <<*itt <<", "; cerr <<"\n"; }}
#else
#define debug(...) (__VA_ARGS__)
#define debugv(x)
#define cerr if(0)cout
#endif
#define next ____next
#define prev ____prev
#define left ____left
#define hash ____hash
typedef long long ll;
typedef long double LD;
typedef pair<int, int> PII;
typedef pair<ll, ll> PLL;
typedef vector<int> VI;
typedef vector<VI> VVI;
typedef vector<ll> VLL;
typedef vector<pair<int, int> > VPII;
typedef vector<pair<ll, ll> > VPLL;
template<class C> void mini(C&a4, C b4){a4=min(a4, b4); }
template<class C> void maxi(C&a4, C b4){a4=max(a4, b4); }
template<class T1, class T2>
ostream& operator<< (ostream &out, pair<T1, T2> pair) { return out << "(" << pair.first << ", " << pair.second << ")";}
template<class A, class B, class C> struct Triple { A first; B second; C third;
bool operator<(const Triple& t) const { if (st != t.st) return st < t.st; if (nd != t.nd) return nd < t.nd; return rd < t.rd; } };
template<class T> void ResizeVec(T&, vector<int>) {}
template<class T> void ResizeVec(vector<T>& vec, vector<int> sz) {
vec.resize(sz[0]); sz.erase(sz.begin()); if (sz.empty()) { return; }
for (T& v : vec) { ResizeVec(v, sz); }
}
typedef Triple<int, int, int> TIII;
template<class A, class B, class C>
ostream& operator<< (ostream &out, Triple<A, B, C> t) { return out << "(" << t.st << ", " << t.nd << ", " << t.rd << ")"; }
template<class T> ostream& operator<<(ostream& out, vector<T> vec) { out<<"("; for (auto& v: vec) out<<v<<", "; return out<<")"; }
template<class T> ostream& operator<<(ostream& out, set<T> vec) { out<<"("; for (auto& v: vec) out<<v<<", "; return out<<")"; }
template<class L, class R> ostream& operator<<(ostream& out, map<L, R> vec) { out<<"("; for (auto& v: vec) out<<v<<", "; return out<<")"; }
void find_pair(int N, std::vector<int> U, std::vector<int> V, int A, int B) {
#define int long long
int M = SZ(U);
vector<int32_t> zeros(M);
int best = ask(zeros);
function<int(VI)> Binuj = [&](VI order) {
int kl = 0, kp = N - 1, faj = N - 1;
while (kl <= kp) {
VI is_forb(N);
int aktc = (kl + kp) / 2;
FOR (i, aktc, N - 1) {
is_forb[order[i]] = 1;
}
VI to_ask(M);
REP (i, M) {
if (is_forb[U[i]] || is_forb[V[i]]) {
to_ask[i] = 1;
}
}
if (ask(to_ask) == best) {
kp = aktc - 1;
} else {
kl = aktc + 1;
faj = order[aktc];
}
}
return faj;
};
VVI slo(N);
REP (i, M) {
slo[U[i]].PB(V[i]);
slo[V[i]].PB(U[i]);
}
function<vector<int32_t>(int)> Bfs = [&](int root) {
VI dis(N, N);
dis[root] = 0;
vector<int32_t> que{(int32_t)root};
for (int ii = 0; ii < SZ(que); ii++) {
int v = que[ii];
for (auto nei : slo[v]) {
if (dis[nei] == N) {
dis[nei] = dis[v] + 1;
que.PB(nei);
}
}
}
return que;
};
vector<int32_t> order(N);
iota(ALL(order), 0);
int any = Binuj(order);
order = Bfs(any);
int s = Binuj(order);
order = Bfs(s);
int t = Binuj(order);
answer(s, t);
}
