using System;
using System.Diagnostics;
using System.Reflection;

class Program
{
    static void Main()
    {
        int n = ni();
        long[][] co = nml(n);

        long O = 500000000000000000L;

        List<int[]> ret = new List<int[]>();
        long lmin = O*2;
        int argmin = -1;
        for(int i = 0;i < n;i++){
            long x = (co[0][0] + co[i][0]) / 2;
            long y = (co[0][1] + co[i][1]) / 2;
            long d = Math.Abs(x - O) + Math.Abs(y - O);
            if(d < lmin){
                lmin = d;
                argmin = i;
            }
        }
        if(argmin > 0){
            long xx = (co[0][0] + co[argmin][0]) / 2;
            long yy = (co[0][1] + co[argmin][1]) / 2;
            co[0][0] = co[argmin][0] = xx;
            co[0][1] = co[argmin][1] = yy;
            ret.Add(new int[]{0, argmin});
        }

        long tx = O*2 - co[0][0];
        long ty = O*2 - co[0][1];

        long[][] cco = co.Skip(1).ToArray();

        double best = Double.PositiveInfinity;
        long[][] barg = new long[32][];

        Random gen = new Random();
        Stopwatch sw = Stopwatch.StartNew();
        while(sw.ElapsedMilliseconds < 800){
            long[][] sel = cco.OrderBy(x => gen.Next()).Take(32).ToArray();
            double x = 0, y = 0;
            for(int i = 0;i < 32;i++){
                x += sel[i][0];
                y += sel[i][1];
            }
            x /= 32;
            y /= 32;
            double d = Math.Max(Math.Abs(x - tx), Math.Abs(y - ty));
            if(d < best){
                best = d;
                barg = sel;
            }
        }

        for(int d = 1;d <= 16;d*=2){
            for(int i = 0;i < 32;i+=d*2){
                ret.Add(new int[]{(int)barg[i][2], (int)barg[i+d][2]});
            }
        }

        // Console.WriteLine($"arg {arg} {vald}");
        ret.Add(new int[]{0, (int)barg[0][2]});

        Console.WriteLine(ret.Count);
        foreach(int[] r in ret){
            Console.WriteLine($"{r[0]+1} {r[1]+1}");
        }

        // long lx = (co[0][0] + co[arg][0]) / 2;
        // long ly = (co[0][1] + co[arg][1]) / 2;
        // Console.WriteLine($"last: {lx} {ly}");
    }

    static double min;
    static List<int> best = new List<int>();

    static void simulate(double[] a, int rem, List<int> route)
    {
        for(int i = 0;i < 4;i++){
            if(Math.Abs(a[i]) < min){
                min = Math.Abs(a[i]);
                best = new List<int>(route);
            }            
        }
        if(rem == 0)return;
        for(int i = 0;i < 3;i++){
            if(a[i] == a[i+1])continue;
            double[] b = (double[])a.Clone();
            double v = (b[i] + b[i+1]) / 2;
            b[i] = b[i+1] = v;
            route.Add(i);
            simulate(b, rem-1, route);
            route.RemoveAt(route.Count-1);
        }
    }

    static string ns()
    {
        return Console.ReadLine();
    }

    static int ni()
    {
        return Convert.ToInt32(ns());
    }

    static int[] na()
    {
        return ns().Split(' ').Select(int.Parse).ToArray();
    }

    static long[] nal()
    {
        return ns().Split(' ').Select(long.Parse).ToArray();
    }

    static long[][] nml(int n)
    {
        long[][] ret = new long[n][];
        for (int i = 0; i < n; i++)
        {
            long[] f = nal();
            ret[i] = new long[]{f[0], f[1], i};
        }
        return ret;
    }
}