#include <bits/stdc++.h>
using namespace std;

random_device rnd;
mt19937 mt(rnd());

int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);

    int N; N = 65535+65534;
    vector<vector<int>> Graph(N);

    int p = 65535;
    for(int i=0; i<65535; i++){
        if(i*2+1 >= 65535){
            Graph.at(i).push_back(Graph.size());
            Graph.push_back({i});
            N++;
        }
        else{
            Graph.at(i).push_back(p);
            Graph.at(p).push_back(i);
            Graph.at(i*2+1).push_back(p);
            Graph.at(p).push_back(i*2+1);
            p++;

            Graph.at(i).push_back(p);
            Graph.at(p).push_back(i);
            Graph.at(i*2+2).push_back(p);
            Graph.at(p).push_back(i*2+2);
            p++;
        }
    }
    
    cout << N << endl;
    for(int i=0; i<N; i++){
        for(auto to : Graph.at(i)){
            if(to < i) continue;
            cout << i+1 << " " << to+1 << endl;
        }
    }

}