import java.util.*
import kotlin.math.*
fun main(){
  val N = readLine()!!.toInt()
  val cardList = mutableListOf<Pair<Long,Long>>()
  repeat(N){
    val (a,b) = readLine()!!.split(" ").map{it.toLong()}
    cardList.add(Pair(a,b))
  }
  val c = 500000000000000000L
  val rlist = mutableListOf<Pair<Int,Double>>()
  var zIdx = -1
  for(i in 0..N-1){
    val fValue = abs(cardList[i].first-c).toDouble()
    val bValue = abs(cardList[i].second-c).toDouble()
    rlist.add(Pair(i,sqrt(fValue*fValue+bValue*bValue)))
  }
  rlist.sortBy{it.second}
  for(i in 0..N-1){
    if(rlist[i].first==0)zIdx=i
  }
  val ansList = mutableListOf<Pair<Int,Int>>()

  val g = cardList.toMutableList()
  val zFront = g[0].first.toDouble()
  val zBack  = g[0].second.toDouble()
  val baseDist = sqrt(zFront*zFront+zBack*zBack)
  for(i in 0..(N-1)/2-1){
    if(2*i+1<zIdx)continue
    val xFront = g[rlist[2*i].first].first.toDouble()
    val xBack  = g[rlist[2*i].first].second.toDouble()
    val yFront = g[rlist[2*i+1].first].first.toDouble()
    val yBack  = g[rlist[2*i+1].first].second.toDouble()
    val nFront = (xFront+yFront)/2.0
    val nBack = (xBack+yBack)/2.0
    val newDist = sqrt(nFront*nFront+nBack*nBack)
    if(newDist<baseDist){
      ansList.add(Pair(rlist[2*i].first,rlist[2*i+1].first))
      val nPair = Pair(nFront.toLong(),nBack.toLong())
      g[rlist[2*i].first]=nPair
      g[rlist[2*i+1].first]=nPair
    }
  }
  val slist = mutableListOf<Pair<Int,Double>>()
  for(i in 0..N-1){
    val fValue = abs(g[i].first-c).toDouble()
    val bValue = abs(g[i].second-c).toDouble()
    slist.add(Pair(i,sqrt(fValue*fValue+bValue*bValue)))
  }
  slist.sortBy{it.second}

  val stack = ArrayDeque<Int>()
  var count = ansList.size
  for(i in 0..N-1){
    if(count>=50)break
    if(slist[i].first==0)break
    stack.add(slist[i].first)
    count++
  }
  for(i in 0..stack.size-1){
    val p = stack.removeLast()
    ansList.add(Pair(0,p))
  }
  println(ansList.size)
  for(i in 0..ansList.size-1){
    val u = ansList[i].first+1
    val v = ansList[i].second+1
    println("$u $v")
  }
}