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#include <bits/stdc++.h>
using namespace std;

#define FOR(i, a, b) for(int i = (a); i <= (b); ++i)
#define REP(i, n) for(int i = 0; i < (n); ++i)
#define ff first
#define ss second

using ll = long long;
using pii = pair<int, int>;

template<class T> int size(T && a) {
	return (int)(a.size());
}
ostream& operator << (ostream &os, string str) {
    for(char c : str) os << c;
    return os;
}
template <class A, class B> ostream& operator << (ostream &os, const pair<A, B> &p) {
	return os << '(' << p.ff << "," << p.ss << ')';
}
template <class T> auto operator << (ostream &os, T &&x) -> decltype(x.begin(), os) {
	os << '{';
	for(auto it = x.begin(); it != x.end(); ++it)
		os << *it << (it == prev(x.end()) ? "" : " ");
	return os << '}';
}
template <class T> ostream& operator << (ostream &os, vector<vector<T>> vec) {
    for(auto x : vec)
    	os << "\n  " << x;
    return os;
}
void dump() {}
template <class T, class... Args> void dump(T &&x, Args... args) {
    cerr << x << "; ";
    dump(args...);
}
#ifdef DEBUG
# define debug(x...) cerr << "[" #x "]: ", dump(x), cerr << '\n'
#else 
# define debug(...) 0
#endif

//--------------------------------------------------

vector<pii> nodes;
int last = 0;

void create_chain(int n) {
	nodes = vector<pii>(n, pair(-1, -1));

	FOR(i, 1, n-1) {
		nodes[i] = pair(i-1, size(nodes));
		nodes.emplace_back(pair(i-1, -1));
	}
}

int prv = -1;
void connect(int p) {
	nodes.emplace_back(prv, p);
	prv = size(nodes)-1;
}

int main() {
	ios_base::sync_with_stdio(0);
	cin.tie(0);

	int k; cin >> k;


	create_chain(32);

	for(int p = 0; k > 0; ++p) {
		if(k & (1 << p)) {
			connect(p);
			k ^= (1 << p);
		}
	}

	reverse(nodes.begin(), nodes.end());
	int n = size(nodes);
	cout << n << '\n';
	for(auto [a, b] : nodes) {
		cout << (a == -1 ? -1 : n-a) << ' ' << (b == -1 ? -1 : n-b) << '\n';
	}

	debug(size(nodes));
}