#include <string.h>
#include <algorithm>
#include <array>
#include <bitset>
#include <cassert>
#include <cfloat>
#include <climits>
#include <cmath>
#include <complex>
#include <ctime>
#include <deque>
#include <fstream>
#include <functional>
#include <iomanip>
#include <iostream>
#include <iterator>
#include <list>
#include <map>
#include <memory>
#include <queue>
#include <random>
#include <set>
#include <stack>
#include <string>
#include <unordered_map>
#include <unordered_set>
#include <utility>
#include <vector>
using namespace std;

int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    cout << 7001 << "\n";
    for(int i = 2; i <= 7001; i += 7) {
        cout << 1 << " " << i << endl;
        cout << i << " " << i+1 << endl;
        cout << i << " " << i+2 << endl;
        cout << i << " " << i+3 << endl;
        cout << i+1 << " " << i+4 << endl;
        cout << i+2 << " " << i+5 << endl;
        cout << i+3 << " " << i+6 << endl;
    }
}