#include "highway.h"
#include<bits/stdc++.h>
using namespace std;
using ll = long long;
long long ask(const std::vector<int> &w);
void answer(int s, int t);
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<int> L) {
vector<int> w(M, 0);
for(auto x : L) w[x] = 1;
return ask(w);
};
auto bfs = [&](int s) -> array<vector<int>, 2> {
vector<int> d(N, 0), p(N, 0);
queue<int> q;
q.push(s), d[s] = 1;
while(!q.empty()) {
int u = q.front(); q.pop();
for(auto [x, id] : v[u]) if(!d[x]) q.push(x), d[x] = d[u]+1, p[x] = id;
}
for(auto &x : d) x--;
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<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<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);
}
