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#include <bits/stdc++.h>

using namespace std;

typedef long long ll;
typedef long double ld;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
typedef vector<bool> vb;
typedef vector<int> vi;
typedef vector<vector<int>> vvi;
typedef vector<ll> vl;
typedef vector<vector<ll>> vvl;
#define pb push_back
#define eb emplace_back
#define mp make_pair
#define mt make_tuple
#define st first
#define nd second
#define FOR(__VAR, __START, __END) for(int __VAR=__START; __VAR<=__END; __VAR++)
#define FORB(__VAR, __START, __END) for(int __VAR=__START; __VAR>=__END; __VAR--)
#define FORK(__VAR, __START, __END, __DIFF) for(int __VAR=__START; __VAR<=END; __VAR+=__DIFF)
#define all(__VAR) (__VAR).begin(), (__VAR).end()
#define rall(__VAR) (__VAR).rbegin(), (__VAR).rend()
#define DEBUG(__VAR) cout << #__VAR << ": " << __VAR << endl;

template<typename __T1, typename __T2>
ostream & operator<<(ostream &out, pair<__T1, __T2> &__VAR)
{
	cout << "[" << __VAR.st << ", " << __VAR.nd << "]";
	return out;
}

template<typename __T>
ostream & operator<<(ostream &out, vector<__T> &__VAR)
{
	cout << "[";
	FOR(i, 0, (int)__VAR.size()-2)
		cout << __VAR[i] << ", ";
	if(__VAR.size()>0)
		cout << __VAR[__VAR.size()-1];
	cout << "]" << endl;
	
	return out;
}

const int INF=1e9;

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

	int k;
	cin >> k;
	int K=k;
	int n=59+__builtin_popcount(k);
	vector<pii> g(n+1, {-1,-1});
	queue<int> que;
	for(int i=n-59+1; i<n; i+=2)
		if(i+2<=n)
			g[i].nd=i+2;
	for(int i=n-59+1; i<n; i++)
		if(i+1<=n)
			g[i].st=i+1;
	for(int i=n; i>=0 && k>0; i-=2,k/=2)
		if(k&1)
			que.push(i);
	for(int i=n-59; i>1; i--) {
		int a=que.front();
		que.pop();
		int b=que.front();
		que.pop();
		g[i]={a,b};
		que.push(i);
	}
	if(__builtin_popcount(K)==1)
		g[1].st=que.front();
	else
		g[1].st=2;
	
	cout << n << '\n';
	for(int i=1; i<=n; i++)
		cout << g[i].st << ' ' << g[i].nd << '\n';

	return 0;
}