#include "doll.h"
#include<bits/stdc++.h>
using namespace std;
typedef vector<int> vi;
#define pb emplace_back
#define SZ(x) (int)x.size()
inline int MSB(unsigned int x){
return 32-__builtin_clz(x);
}
int c=-1;
vi C,X,Y;
vi occ[100100];
void fill(int x, int occnum, int skip, int startind){
if (x == 2){
X.pb(occ[occnum][startind]);
Y.pb(occ[occnum][skip + startind]);
return;
}
}
void create_circuit(int M, std::vector<int> A) {
int N = A.size();
C.resize(M+1,0);
occ[0].pb(A[0]);
for (int i=0;i<N-1;++i){
occ[A[i]].pb(A[i+1]);
}
occ[A[N-1]].pb(0);
for (int i=0;i<=M;++i){
if (SZ(occ[i]) == 0)continue;
if (SZ(occ[i]) == 1){
C[i] = occ[i][0];
}else{
C[i] = c--;
fill(SZ(occ[i]), i, 1, 0);
}
}
// for (int i=0;i<=M;++i)cout<<C[i]<<' ';cout<<'\n';
answer(C,X,Y);
}
