#include <bits/stdc++.h>
using namespace std;
//#include <atcoder/all>
//using namespace atcoder;
//using mint = modint998244353;

//多倍長整数//
//#include <boost/multiprecision/cpp_int.hpp>
//namespace mp = boost::multiprecision;
//using Bint = mp::cpp_int;

const int INF = 1e9;
const int MOD = 998244353;
const long long LINF = 4e18;

using ll = long long;
using vi = vector<int>;
using vl = vector<long long>;
using vs = vector<string>;
using vc = vector<char>;
using vb = vector<bool>;
using vvi = vector<vector<int>>;
using vvvi = vector<vector<vector<int>>>;
using vvvvi = vector<vector<vector<vector<int>>>>;
using vvl = vector<vector<long long>>;
using vvvl = vector<vector<vector<long long>>>;
using vvvvl = vector<vector<vector<vector<long long>>>>;
using vvc = vector<vector<char>>;
using vvb = vector<vector<bool>>;
using vvvb = vector<vector<vector<bool>>>;
using vvvvb = vector<vector<vector<vector<bool>>>>;

#define rep(i, n) for (int i = 0; i < (int)(n); i++)
#define dump(x)  cout << #x << " = " << (x) << endl;
#define Yes(n) cout << ((n) ? "Yes" : "No"  ) << endl
#define ALL(obj) (obj).begin(),(obj).end()

int main(){
	ios::sync_with_stdio(false);
	cin.tie(nullptr);
	cout << 8005 << endl;
	cout << 1 << ' ' << 3 << "\n";
	cout << 2 << ' ' << 3 << "\n";
	rep(i,1000){
		int cur = 8*i + 3;
		cout << cur << ' ' << cur + 1 << "\n";
		cout << cur + 2 << ' ' << cur + 3 << "\n";
		cout << cur + 3 << ' ' << cur + 4 << "\n";
		cout << cur + 1 << ' ' << cur + 3 << "\n";
		cout << cur + 1 << ' ' << cur + 6 << "\n";
		cout << cur + 5 << ' ' << cur + 6 << "\n";
		cout << cur + 6 << ' ' << cur + 7 << "\n";
		cout << cur + 1 << ' ' << cur + 8 << "\n";
	}
	cout << 8003 << ' ' << 8004 << "\n";
	cout << 8003 << ' ' << 8005 << "\n";
	return 0;
}