#include "doll.h"
#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef pair <ll, ll> pii;
#define precision(n) fixed << setprecision(n)
#define pb push_back
#define ub upper_bound
#define lb lower_bound
#define mp make_pair
#define eps (double)1e-9
#define PI 2*acos(0.0)
#define endl "\n"
#define sz(v) (int)(v).size()
#define all(v) v.begin(),v.end()
#define rall(v) v.rbegin(),v.rend()
#define do_not_disturb ios::sync_with_stdio(0);cin.tie(0);cout.tie(0);
vector <vector <int>> after;
vector <int> connected, x, y;
void create_circuit(int M, vector<int> A){
int i;
after.resize(M+1);
connected.resize(M+1);
A.pb(0);
connected[0] = A[0];
int n = sz(A);
for(i = 0; i < n-1; i++){
after[A[i]].pb(A[i+1]);
}
int s = 0;
for(i = 1; i <= M; i++){
auto saizu = sz(after[i]);
if(!saizu){
}
else if(saizu == 1){
connected[i] = after[i][0];
}
else if(saizu == 2){
connected[i] = --s;
x.pb(after[i][0]);
y.pb(after[i][1]);
}
else if(saizu <= 4){
connected[i] = --s;
x.pb(--s);
y.pb(--s);
if(saizu == 4){
x.pb(after[i][0]);
y.pb(after[i][2]);
x.pb(after[i][1]);
y.pb(after[i][3]);
}
else{
x.pb(connected[i]);
y.pb(after[i][1]);
x.pb(after[i][0]);
y.pb(after[i][2]);
}
}
}
/*
for(auto to : connected) cout << to << ' ';
cout << endl;
for(i = 0; i < sz(x); i++) cout << x[i] << ' ' << y[i] << endl;
*/
answer(connected, x, y);
}
