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 n = NN;
        var ans = new List<int[]>();
        for (var i = 1; i < n; ++i)
        {
            for (var j = i + 1; j < n - i + 1; ++j) ans.Add(new int[] { i, j });
        }
        WriteLine(string.Join("\n", ans.Select(ai => string.Join(" ", ai))));
    }
}