using System;
using static System.Console;
using System.Linq;
using System.Collections.Generic;

class Program
{
    static int NN => int.Parse(ReadLine());
    static long[] NList => ReadLine().Split().Select(long.Parse).ToArray();
    static long[][] NArr(long n) => Enumerable.Repeat(0, (int)n).Select(_ => NList).ToArray();
    public static void Main()
    {
        Solve();
    }
    static void Solve()
    {
        var ans = new List<string>();
        ans.Add("99");
        for (var i = 0; i < 99; ++i) ans.Add($"{i + 1} {i + 2}");
        WriteLine(string.Join("\n", ans));
    }
}