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// tested by Hightail: https://github.com/dj3500/hightail
#include <bits/stdc++.h>
using namespace std;
#define pb push_back
#define INF 1001001001
#define FOR(i,n) for(int i=0;(i)<(n);++(i))
#define FORI(i,n) for(int i=1;(i)<=(n);++(i))
#define mp make_pair
#define pii pair<int,int>
#define ll long long
#define vi vector<int>
#define SZ(x) ((int)((x).size()))
#define fi first
#define se second
#define wez(n) int n; scanf("%d",&(n));
#define wez2(n,m) int n,m; scanf("%d %d",&(n),&(m));
#define wez3(n,m,k) int n,m,k; scanf("%d %d %d",&(n),&(m),&(k));
inline void pisz(int n) { printf("%d\n",n); }
template<typename T,typename TT> ostream& operator<<(ostream &s,pair<T,TT> t) {return s<<"("<<t.first<<","<<t.second<<")";}
template<typename T> ostream& operator<<(ostream &s,vector<T> t){FOR(i,SZ(t))s<<t[i]<<" ";return s; }
#define DBG(vari) cout<<"["<<__LINE__<<"] "<<#vari<<" = "<<(vari)<<endl;
#define ALL(t) t.begin(),t.end()
#define FOREACH(i,t) for (__typeof(t.begin()) i=t.begin(); i!=t.end(); i++)
#define TESTS wez(testow)while(testow--)
#define REP(i,a,b) for(int (i)=(a);(i)<=(b);++i)
#define REPD(i,a,b) for(int (i)=(a); (i)>=(b);--i)
#define REMAX(a,b) (a)=max((a),(b));
#define REMIN(a,b) (a)=min((a),(b));
#define IOS ios_base::sync_with_stdio(0);

const int N = 111;
int a1[N], a2[N];

int go (int k, int a) {
   if (k == 1) {
      a1[a] = a+1;
      a2[a] = -1;
      a1[a+1] = a2[a+1] = -1;
      return a+1;
   }
   if (k & 1) {
      int n = go(k-1,a+1);
      a1[a] = a+1;
      a2[a] = n;
      return n;
   }
   // k parzyste
   a1[a] = a+1;
   a2[a] = a+2;
   a1[a+1] = a+2;
   a2[a+1] = -1;
   return go(k/2,a+2);
}

int main () {
   wez(k);
   int n = go(k,1);
   pisz(n);
   FORI(i,n) printf("%d %d\n", a1[i], a2[i]);
}