#include "highway.h"
#include<bits/stdc++.h>
using namespace std;
using ll = long long;
void find_pair(int N, vector<int> U, vector<int> V, int A, int B) {
int M = U.size();
vector<vector<array<int, 2>>> v(N);
for(int i=0;i<M;i++) {
v[U[i]].push_back({V[i], i});
v[V[i]].push_back({U[i], i});
}
auto query = [&](vector<vector<int>> L) {
vector<int> w(M, 0);
for(auto v : L) for(auto x : v) w[x] = 1;
return ask(w);
};
auto bfs = [&](int s) -> pair<vector<int>, vector<vector<int>>> {
vector<int> d(N, -1);
vector<vector<int>> p(N);
queue<int> q;
q.push(s), d[s] = 0;
while(!q.empty()) {
int u = q.front(); q.pop();
for(auto [x, id] : v[u]) {
if(d[x] == -1) q.push(x), d[x] = d[u]+1;
if(d[x] == d[u]+1) p[x].push_back(id);
}
}
return {d, p};
};
ll D = query({});
auto find_deepest = [&](int s) {
auto [d, p] = bfs(s);
vector<array<int, 2>> L(N);
for(int i=0;i<N;i++) L[i] = {d[i], i};
sort(L.rbegin(), L.rend());
vector<vector<int>> P(N);
for(int i=0;i<N;i++) P[i] = p[L[i][1]];
int l = 1, r = N-1;
while(l <= r) {
int mid = (l+r) >> 1;
if(query(vector<vector<int>>(P.begin(), P.begin()+mid)) == D) l = mid+1;
else r = mid-1;
}
return L[r][1];
};
int P = find_deepest(0);
int S = find_deepest(P);
int T = find_deepest(S);
answer(S, T);
}
