import java.util.Scanner

import scala.collection.{mutable => mu}

object Problem202 {

  type Index = (Int, Int)
  type Point = (Int, Int)

  def overlap(a: Point, b: Point): Boolean = {
    Math.pow(a._1 - b._1, 2.0) + Math.pow(a._2 - b._2, 2.0) < 400
  }

  def proc(coins: Seq[Point]): Int = {

    val S = new mu.HashMap[Index, mu.HashSet[Point]]()

    def overlapCoin(coin: Point, index: Index): Boolean = {
      val (px, py) = (index._1, index._2)
      for {
        pxi <- px - 1 to px + 1
        pyi <- py - 1 to py + 1
        points <- S.get(pxi, pyi)
        point <- points
        if overlap(coin, point)
      } {
        return true
      }
      false
    }

    def putCoin(coin: Point): Unit = {
      val index = (coin._1 / 20, coin._2 / 20)

      if (!overlapCoin(coin, index)) {
        if (!S.contains(index)) {
          S += index -> mu.HashSet[Point]()
        }
        S(index) += coin
      }
    }

    coins.foreach { coin =>
      putCoin(coin)
    }
    S.map(_._2.size).sum
  }

  def main(args: Array[String]) {
    val sc = new Scanner(System.in)
    val n = sc.nextInt()
    val coins = Array.fill(n)((sc.nextInt(), sc.nextInt()))

    val result = proc(coins)
    println(result)
  }
}