[문제 링크]

https://www.acmicpc.net/problem/11729

[입출력 예]

[소스코드]

#include <bits/stdc++.h>
using namespace std;
 
void func(int a, int b, int n){
  if (n==1){ cout<<a<<" "<<b<<'\n';
  return;}
  func(a,6-a-b,n-1);
  cout<<a<<" "<<b<<"\n";
  func(6-a-b,b,n-1);
}
 
 
int main(){
  ios::sync_with_stdio(0);
  cin.tie(0);
 
  int n;
  cin>>n;
  cout<<(1<<n)-1<<'\n';
  func(1,3,n);
  return 0;
}