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#include <bits/stdc++.h>

using namespace std;

int k,l,a,b;
vector <int> u;
vector <int> v[101];

int main()
{
	scanf("%d",&k);
	while (k>0)
	{
		if (k%2) 
		{
			u.push_back(1);
			k--;
		}
		else
		{
			u.push_back(0);
			k/=2;
		}
	}
	v[1].push_back(2);
	l=3;
	a=1;
	b=2;
	for (int i=u.size()-2; i>=0; i--)
	{
		if (u[i])
		{
			v[a].push_back(l);
			v[l].push_back(b);
			a=l;
			l++;
		}
		else
		{
			v[b].push_back(l);
			v[b].push_back(l+1);
			v[l].push_back(l+1);
			b=l+1;
			l+=2;
		}
	}
	v[b].push_back(l);
	printf("%d\n",l);
	for (int i=1; i<=l; i++)
	{
		if (v[i].size()==0)
		{
			printf("-1 -1\n");
		}
		else if (v[i].size()==1)
		{
			printf("%d -1\n",v[i][0]);
		}
		else
		{
			printf("%d %d\n",v[i][0],v[i][1]);
		}
		
	}
}