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#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;

#define sim template <class c
#define ris return *this
#define dor > debug &operator<<
#define eni(x)                                                                    \
    sim > typename enable_if<sizeof dud<c>(0) x 1, debug &>::type operator<<(c i) \
    {
sim > struct rge
{
    c b, e;
};
sim > rge<c> range(c i, c j) { return rge<c>{i, j}; }
sim > auto dud(c *x) -> decltype(cerr << *x, 0);
sim > char dud(...);
struct debug
{
#ifdef XOX
    ~debug()
    {
        cerr << endl;
    }
    eni(!=) cerr << boolalpha << i;
    ris;
} eni(==) ris << range(begin(i), end(i));
}
sim, class b dor(pair<b, c> d)
{
    ris << "" << d.first << " --> " << d.second << "";
}
sim dor(rge<c> d)
{
    *this << "[";
    for (auto it = d.b; it != d.e; ++it)
        *this << ", " + 2 * (it == d.b) << *it;
    ris << "]";
}
#else
    sim dor(const c &)
    {
        ris;
    }
#endif
}
;
#define imie(...) "" << #__VA_ARGS__ " = " << (__VA_ARGS__) << ", "

#define F first
#define S second
#define endl '\n'
#define pb emplace_back
#define mp make_pair
#define gcd(a, b) __gcd(a, b)
#define lcm(a, b) (a * b) / gcd(a, b)
#define all(v) (v).begin(), (v).end()
#define lb(v, val) (lower_bound((v).begin(), (v).end(), val) - (v).begin())
#define ub(v, val) (upper_bound((v).begin(), (v).end(), val) - (v).begin())
#define fast                      \
    ios_base::sync_with_stdio(0); \
    cin.tie();                    \
    cout.tie()
#define vt vector
#define sz(v) (int)(v).size()
using ll = long long;
using pii = pair<int, int>;

typedef tree<
    int,
    null_type,
    less<int>,
    rb_tree_tag,
    tree_order_statistics_node_update>
    oset;

const int kax = __lg((int)1e9);
//! TYLKO DLA K & 1

int main()
{
    fast;
    int k;
    cin >> k;
    vt<int> bits;
    vt<vt<int>> adj(101);
    for (int b = 0; b <= kax; b++)
        if (k & (1 << b))
            bits.pb(1 << b);
    debug() << imie(bits);
    set<int> avail;
    for (int i = 2; i <= 99; i++)
        avail.insert(i);
    int pointer = 0;
    int parent = 1;
    int sofar = 1;
    while (pointer != sz(bits))
    {
        adj[parent].pb(*avail.begin());
        avail.erase(avail.begin());
        adj[parent].pb(*avail.begin());
        avail.erase(avail.begin());
        // debug() << imie(adj[parent]);
        if (sofar == bits[pointer])
        {
            pointer++;
            adj[adj[parent][1]].pb(100);
        }
        int nxt = *avail.begin();
        avail.erase(avail.begin());
        adj[adj[parent][0]].pb(nxt);
        adj[adj[parent][1]].pb(nxt);
        sofar *= 2;
        parent = nxt;
    }
    for (auto &a : adj)
        while (sz(a) != 2)
            a.pb(-1);
    cout << 100 << endl;
    for (int i = 1; i <= 100; i++)
        cout << adj[i][0] << " " << adj[i][1] << endl;
}