package yukicoder

object Main {
  def main(args: Array[String]): Unit = {
    val n = io.StdIn.readLine().toInt
    val xys = (for (i <- 1 to n) yield
      io.StdIn.readLine().split(' ').map(_.toInt)).toList
    val gs = genCommutativeGroup(xys)
    val ans = n match {
      case 0 => 1.0
      case _ => {
        Math.sqrt(gs.map(maxDistance).max) + 2.0
      }
    }
    println(ans)
  }

  def distance2(p1: Array[Int], p2: Array[Int]): Double =
    Math.pow(p1(0) - p2(0), 2) + Math.pow(p1(1) - p2(1), 2)


  def commutable(p1: Array[Int], p2: Array[Int]): Boolean = {
    distance2(p1, p2) <= 100
  }


  def commutableGroup(xys: List[Array[Int]] , p1: Array[Int]): List[Array[Int]] = {
    if(xys.isEmpty) Nil else {
      val g = xys.filter(p2 => commutable(p1, p2))
      val next = xys.diff(g)
      g ++ g.flatMap(commutableGroup(next, _))
    }
  }


  def genCommutativeGroup(ps: List[Array[Int]]): List[List[Array[Int]]] = {
    ps match {
      case h :: t => {
        val g = commutableGroup(ps, h)
        g :: genCommutativeGroup(t.diff(g))
      }
      case _ => Nil
    }
  }


  def maxDistance(g: List[Array[Int]]): Double = {
    (for (i <- g; j <- g) yield distance2(i, j)).max
  }


}