using System;
using System.ComponentModel.DataAnnotations;
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();
        long[] last = new long[0];

        Random gen = new Random();
        int ct = 0;
        for(int rep = 0;rep < 16;rep++){
            double best = Double.PositiveInfinity;
            long[][] barg = new long[4][];
            Stopwatch sw = Stopwatch.StartNew();
            while(sw.ElapsedMilliseconds < 50){
                bool[] used = new bool[cco.Length];
                long[][] sel = new long[4][];
                for(int i = 0;i < 4;i++){
                    while(true){
                        int t = (int)(gen.NextInt64() % cco.Length);
                        if(used[t])continue;
                        sel[i] = cco[t];
                        used[t] = true;
                        break;
                    }
                }
                // long[][] sel = cco.OrderBy(x => gen.Next()).Take(4).ToArray();
                double x = 0, y = 0;
                for(int i = 0;i < 4;i++){
                    x += sel[i][0];
                    y += sel[i][1];
                }
                x /= 4;
                y /= 4;
                double d = Math.Max(Math.Abs(x - tx), Math.Abs(y - ty));
                if(d < best){
                    best = d;
                    barg = sel;
                }
                ct++;
            }

            for(int d = 1;d <= 2;d*=2){
                for(int i = 0;i < 4;i+=d*2){
                    long x = (barg[i][0] + barg[i+d][0]) / 2;
                    long y = (barg[i][1] + barg[i+d][1]) / 2;
                    barg[i][0] = barg[i+d][0] = x;
                    barg[i][1] = barg[i+d][1] = y;
                    ret.Add(new int[]{(int)barg[i][2], (int)barg[i+d][2]});
                }
            }
            last = barg[0];
        }

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

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

        // Console.WriteLine(ct);

        // long lx = (co[0][0] + last[0]) / 2;
        // long ly = (co[0][1] + last[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;
    }
}