#include "highway.h"
#include <bits/stdc++.h>
#define pii pair<int, int>
#define szof(s) (int)s.size()
#define ll long long
#define fr first
#define sc second
using namespace std;
const int N = 90004;
vector <int> g[N];
int x[N], y[N];
int n, m, a, b;
int S, T;
vector <int> w;
map <pii, bool> mp;
struct SmallSolve {
int dfs(int v, int par) {
for (int to : g[v]) {
if (to == par) {
continue;
}
if (mp.count({v, to})) {
return dfs(to, v);
}
}
return v;
}
void solve(int NN, vector<int> U, vector<int> V, int A, int B) {
n = NN;
m = U.size();
a = A;
b = B;
w.resize(m, 1);
for (int i = 0; i < m; i++) {
x[i] = U[i];
y[i] = V[i];
g[x[i]].push_back(y[i]);
g[y[i]].push_back(x[i]);
}
ll before = ask(w);
for (int i = 0; i < m; i++) {
w[i] = 0;
int nxt = ask(w);
if (nxt < before) {
w[i] = 0;
before = nxt;
} else {
w[i] = 1;
}
}
for (int i = 0; i < m; i++) {
if (w[i] == 0) {
mp[{x[i], y[i]}] = 1;
mp[{y[i], x[i]}] = 1;
}
}
S = 0;
T = dfs(0, -1);
answer(S, T);
}
}subtask1;
struct LineSolve {
vector <int> w;
bool need(int NN, vector<int> U, vector<int> V, int A, int B) {
bool ok = 1;
ok &= (NN - 1 == szof(U));
for (int i = 0; i < szof(U); i++) {
ok &= (U[i] == i && V[i] == i + 1);
}
return ok;
}
void init(int l, int r) {
for (int i = 0; i < m; i++) {
if (l <= i && i <= r) {
w[i] = 0;
} else {
w[i] = 1;
}
}
}
void solve(int NN, vector<int> U, vector<int> V, int A, int B) {
n = NN;
m = U.size();
a = A;
b = B;
w.resize(m, 1);
long long before = ask(w);
for (int i = 0; i < m; i++) {
x[i] = U[i];
y[i] = V[i];
g[x[i]].push_back(y[i]);
g[y[i]].push_back(x[i]);
}
int l = -1, r = m - 1;
while (r - l > 1) {
int mid = (l + r) >> 1;
init(0, mid);
if (ask(w) < before) {
r = mid;
} else {
l = mid;
}
}
S = (l == -1 ? x[0] : y[l]);
l = 0, r = m;
while (r - l > 1) {
int mid = (l + r) >> 1;
init(mid, m - 1);
if (ask(w) < before) {
l = mid;
} else {
r = mid;
}
}
T = (r == m ? y[m - 1] : x[r]);
answer(S, T);
}
}subtask3;
void find_pair(int NN, vector<int> U, vector<int> V, int A, int B) {
if (NN <= 100 && szof(U) == NN - 1) {
subtask1.solve(NN, U, V, A, B);
}
if (subtask3.need(NN, U, V, A, B)) {
subtask3.solve(NN, U, V, A, B);
}
}
/*
10
9
4
9
4
1
4 6
9 5
5 0
8 2
1 7
7 4
4 2
2 9
3 9
*/
