oIJK2x - Online C++ Compiler & Debugging Tool


#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define endl '\n'
ll N = 1e9+7;
ll oo =1e13;
const ll maxx = 1000000 + 3;
ll n,m,k,q,x,y,z,l,r,mid,ans;
stack<ll>a;
stack<ll>b;
stack<ll>c;

vector<pair<int,int>>out;

void go(ll n,ll a,ll b ,ll c) {
    if (n==0)return;
    go(n-1,a,c,b);
    out.push_back({a,c});
    go(n-1,b,a,c);
}
void solve() {
    cin>>n;
    go(n,1,2,3);
    cout<<out.size()<<endl;
    for (auto &i:out)cout<<i.first<<' '<<i.second<<endl;
}
int main() {
    ios_base::sync_with_stdio(false); cin.tie(0); cout.tie(0);
    ll t=1 ;
    // cin >>t;
    while (t--) {
        ans=0;
        solve();
    }
}