#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define ld long double
#define sz(x) x.size()
#define all(x) x.begin(), x.end()
#define rall(x) x.rbegin(), x.rend()
long long ask(const std::vector<int> &w);
void answer(int s, int t);
const int maxN = 1e5 + 10;
vector<pair<int, int>> adj[maxN], g[maxN];
int n, m, u[maxN], v[maxN];
long long a, b;
template<typename F>
void pr(F a) {
cerr << a << endl;
}
template<typename T>
void pr(vector<T>& a) {
cerr << "[ ";
for(auto i: a) {
cerr << i << " ";
}
cerr << "]" << endl;
}
void find_pair(int N, std::vector<int> U, std::vector<int> V, int A, int B) {
n = N, m = sz(U), a = A, b = B;
vector<int> to_ask(m, 0);
long long start = ask(to_ask);
bool flag = true;
for(int i = 0; i < m; i++) {
adj[U[i]].push_back({V[i], i});
adj[V[i]].push_back({U[i], i});
u[i] = U[i], v[i] = V[i];
}
int ina = 0, inb = m - 1, res = -1;
while(ina <= inb) {
int mid = (ina + inb) / 2;
vector<int> toask(m, 0);
for(int i = 0; i <= mid; i++) {
toask[i] = 1;
}
long long ansi = ask(toask);
if(ansi != start) {
res = mid;
inb = mid - 1;
} else {
ina = mid + 1;
}
}
// we get edge
// u[res]: v[res]
vector<int> left, right, all;
vector<bool> vis(n);
queue<pair<int, int>> q;
q.push({u[res], 1});
q.push({v[res], 2});
left.push_back(u[res]);
right.push_back(v[res]);
vis[u[res]] = vis[v[res]] = true;
while(!q.empty()) {
auto u = q.front();
q.pop();
for(auto i: adj[u.first]) {
if(vis[i.first]) continue;
vis[i.first] = true;
if(u.second == 1) {
left.push_back(i.first);
} else {
right.push_back(i.first);
}
q.push({i.first, u.second});
}
}
// pr(left);
// pr(right);
auto solve = [&](vector<int>& nodes)->int {
int ina = 0, inb = sz(nodes) - 1, res = -1;
while(ina <= inb) {
int mid = (ina + inb) / 2;
vector<int> toask(m, 1), del(n);
for(int i = mid + 1; i < sz(nodes); i++) {
del[nodes[i]] = 1;
}
// pr(del);
for(int i = 0; i < m; i++) {
if(!del[u[i]] && !del[v[i]]) {
toask[i] = 0;
}
}
long long ansi = ask(toask);
// pr(ansi);
// pr(start);
if(ansi == start) {
res = mid;
inb = mid - 1;
} else {
ina = mid + 1;
}
}
// pr(res);
assert(res != -1);
return nodes[res];
};
answer(solve(left), solve(right));
}
