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#include<bits/stdc++.h>
#define VAR(i,n) __typeof(n) i = (n)
#define loop(i,j,s) for(int i=j;i<s;i++)
#define loopback(i,j,s) for(int i=j;i>=s;i--)
#define foreach(i,c) for(VAR(i,(c).begin());i!=(c).end();i++)
#define pln( x ) cout << x << "\n"
#define ps( x ) cout << x << " "
#define entr cout << "\n"
#define pcnt(i) __builtin_popcount(i)
#define ll long long
#define pb push_back
#define mp make_pair
#define ff first
#define ss second
#define SIZE(c) (c).size()
#define ALL(c) (c).begin(), (c).end()
using namespace std;
typedef vector<int> VI;
typedef pair<int, int> PII;
typedef vector<vector<int> > VVI;
const int INFTY=20000000;
const int MAX=110;
const int MOD=10000000;

void coutTab(int* tab,int n){
	loop(i,0,n){
		cout<<tab[i]<<" ";
	}
	cout<<"\n";
}

template<class T> void coutVec(vector<T> tab){
	for(T t : tab){
		cout<<t<<" ";
	}
	cout<<"\n";
}
//------------------------------------------
PII es[MAX];
int bits(int k) {
	int r=0;
	while(k>0) {r++; k/=2;}
	return r;
}
ll dp[MAX];
int main(){
	ios_base::sync_with_stdio(0);
	int k;
	cin>>k;
	int b = bits(k);
	loop(i,0,MAX) es[i]={-1,-1};
	loop(i,1,b+1){
		es[2*i-1]={2*i, 2*i+1};
		es[2*i]={2*i+1,-1};
	}
	int n=2*(b+1);
	int r=1;
	while(k>0) {
		if(k%2==1){
			es[2*r]={es[2*r].ff, n};
		} 
		r++;
		k/=2;
	}
	pln(n);
	loop(i,1,n+1) {
		ps(es[i].ff);pln(es[i].ss);
	}
	
	//dp[1]=1;
	//loop(i,1,n) {
	//	if(es[i].ff!=-1) dp[es[i].ff]+=dp[i];
	//	if(es[i].ss!=-1) dp[es[i].ss]+=dp[i];
	//}
	//pln(dp[n]);
}