// compile: g++ -o data data.cpp -std=gnu++20 -DLOCAL
// run: ./data < data.in
#include <bits/stdc++.h>
#pragma GCC optimize("O3,unroll-loops")
#pragma GCC target("avx2,bmi,bmi2,lzcnt,popcnt")
#ifdef LOCAL
#endif
#define sz(v) ((int)(v).size())
#define PV(v) for (int i=0;i<v.size();++i)cout<<v[i]<<" ";cout<<endl;
#define INTINF 9223372036854775807
#define int long long

using namespace std;

void dfs(int a, int b, int c, int n) {
    // a -> b, temp: c
    if (n == 0) return;
    dfs(a, c, b, n-1);
    cout << a << " " << b << endl;
    dfs(c, b, a, n-1);
}

int32_t main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    cout.tie(nullptr);
    int n; cin >> n;
    cout << (1<<n) - 1 << endl;
    dfs(1, 3, 2, n);

    return 0;
}