#include "doll.h"
#include <bits/stdc++.h>
using namespace std;
/*
void answer(vector <int> c,vector <int> x,vector <int> y){
cout<<"C: ";
for (auto&i:c) cout<<i<<' ';
cout<<endl;
cout<<"X: ";
for (auto&i:x) cout<<i<<' ';
cout<<endl;
cout<<"Y: ";
for (auto&i:y) cout<<i<<' ';
cout<<endl;
return;
}
*/
void create_circuit(int m,vector <int> a){
int cnt[m+1]={};
for (auto&i:a) cnt[i]++;
bool can=1;
for (int i=1; i<=m; i++){
if (cnt[i]>4){
can=0;
break;
}
}
if (can){
vector <int> c(m+1,0),x,y;
c[0]=a[0];
int n=a.size();
a.push_back(0);
vector <int> nxt[m+1];
for (int i=0; i<n; i++) nxt[a[i]].push_back(a[i+1]);
int cur=0;
for (int i=1; i<=m; i++){
if (nxt[i].size()==1){
c[i]=nxt[i][0];
} else if (nxt[i].size()==2){
cur--;
c[i]=cur;
x.push_back(nxt[i][0]);
y.push_back(nxt[i][1]);
} else if (nxt[i].size()==3){
cur--;
c[i]=cur;
cur--;
x.push_back(cur);
cur--;
y.push_back(cur);
x.push_back(c[i]);
y.push_back(nxt[i][1]);
x.push_back(nxt[i][0]);
y.push_back(nxt[i][2]);
} else if (nxt[i].size()==4){
cur--;
c[i]=cur;
cur--;
x.push_back(cur);
cur--;
y.push_back(cur);
x.push_back(nxt[i][0]);
y.push_back(nxt[i][2]);
x.push_back(nxt[i][1]);
y.push_back(nxt[i][3]);
}
}
answer(c,x,y);
return;
}// else {
// for (int i=0; i<=m; i++) c[i]=-1;
//
// }
}
/*
int main(){
int n,m;
cin>>m>>n;
vector <int> a;
for (int i=0; i<n; i++){
int t;
cin>>t;
a.push_back(t);
}
create_circuit(m,a);
}
*/
