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#include <bits/stdc++.h>
#define fi first
#define se second
#define pb push_back

using namespace std;
typedef long long ll;

const int MAXN = 1000*1000 + 7;
const int INF = 1000*1000*1000 + 7;

int G[MAXN][2];

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

	int k;
	cin >> k;
	for(int i = 1; i <= 100; i++)
		G[i][0] = G[i][1] = -1;

	int n = 1;
	while(k > 1)
	{
		G[n][0] = n+1, G[n][1] = n+2;
		G[n+1][0] = n+2;
		if(k % 2)
			G[n+1][1] = 0;
		k /= 2;
		n += 2;
	}
	G[n][0] = n+1;
	for(int i = 1; i <= n; i++)
		if(G[i][1] == 0) G[i][1] = n+1;
	cout << n+1 << '\n';
	for(int i = 1; i <= n+1; i++)
		cout << G[i][0] << ' ' << G[i][1] << '\n';
	return 0;
}