Shared code

/* 777 */
#include "bits/stdc++.h"
using namespace std;

#define int long long 
#define endl '\n'
using vi = vector <int>;
using vii = vector <vi>;
using pii = pair<int,int>;
using vpii = vector<pii>;
#define pb push_back
#define eb emplace_back
#define all(x) x.begin(),x.end()
#define sortf(x) sort(all(x))
#define sortr(x) sort(all(x),greater<int>())

// const int MOD=1e9+7;
// const int inf=1e9;
vi vec;
vpii vecp;
// const int N=1e6;
int n;

void pre(){

}

void tower_of_hanoi(int n,int source, int destination) {
	if (!n) return;
	int helper = 6 - (source + destination);
	tower_of_hanoi(n-1, source, helper);
	// cout << source << " " << destination << endl;
	vecp.eb(source,destination);
	tower_of_hanoi(n-1, helper, destination);
}

void print_vecp(vpii vecp) {
	for (auto &[src, dest]: vecp) {
		cout << src << " " << dest << endl;
	}
}

void solve(){
	cin>>n;
	tower_of_hanoi(n, 1, 3);
	cout << vecp.size() << endl;
	print_vecp(vecp);
}

signed main(){
	ios::sync_with_stdio(false);
	cin.tie(nullptr);
	cout.tie(nullptr);
	pre();
	solve();
}

/*
1 -> 1 3

2
1 -> 1 2
2 -> 1 3
1 -> 2 3

3
1 -> 1 3
2 -> 1 2
1 -> 3 2
3 -> 1 3
1 -> 2 1
2 -> 2 3
1 -> 1 3

4
1 -> 1 2
2 -> 1 3
1 -> 2 3
3 -> 1 2
1 -> 3 1
2 -> 3 2
1 -> 1 2
4 -> 1 3
1 -> 2 3
2 -> 2 1
1 -> 3 1
3 -> 2 3
1 -> 1 2
2 -> 1 3
1 -> 2 3
*/