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//42

#pragma GCC optimize("O3")
#pragma GCC optimize("unroll-loops")

#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>

using namespace std;
using namespace __gnu_pbds;

typedef uint32_t ul;
typedef int32_t l;
typedef uint64_t ull;
typedef int64_t ll;

template <typename T>
using statistics_set = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;

const l INF = 1000000000 + 9;
const ll MOD = 123456789;
const l PRIME = 200003;
const ll L_INF = 1000000000000000000LL + 7;
const double EPS = 1e-5;

#define FOR(x, y, z) for (l z = x; z < y; z++)
#define FORE(x, y, z) for (l z = x; z <= y; z++)
#define FORD(x, y, z) for (l z = x; z > y; z--)
#define FORDE(x, y, z) for (l z = x; z >= y; z--)
#define REP(x, y) for (l y = 0; y < x; y++)
#define ALL(...) (__VA_ARGS__).begin(), (__VA_ARGS__).end()

#define PF push_front
#define POF pop_front
#define PB push_back
#define POB pop_back
#define MP make_pair
#define FS first
#define SC second

const l MAXN = 1000005;

l n=90, k;
l edge[100][2], power[35];

int main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr); cout.tie(nullptr);

    FORE(1, 15, i)
    {
        edge[i][0] = 2*i;
        edge[i][1] = 2*i+1;
    }

    FORE(16, 31, i)
        edge[i][0] = edge[i][1] = -1;

    l idx{32};
    REP(29, i)
    {
        edge[idx][0] = idx+1;
        edge[idx][1] = idx+2;
        edge[idx+1][0] = idx+2;
        edge[idx+1][1] = -1;

        power[29-i] = idx;
        idx += 2;
    }

    power[0] = idx;
    edge[idx][0] = edge[idx][1] = -1;
    n = idx;

    cin >> k;
    l cnt{0};
    idx = 16;

    while(k)
    {
        if(k & 1)
        {
            if(edge[idx][0] == -1)
                edge[idx][0] = power[cnt];

            else
            {
                edge[idx][1] = power[cnt];
                idx++;
            }
            
        }

        k >>= 1;
        cnt++;
    }

    cout << n << "\n";
    FORE(1, n, i)
        cout << edge[i][0] << " " << edge[i][1] << "\n";
}