import scala.io.Source.stdin

object Main {

  def main(args:Array[String]) = {
    val x = 4.9/(9.8*9.8)
    val b = new StringBuilder
    val f = (v:Double) => Math.ceil((x*v*v+5D)/5D).toInt
    for(i<-stdin.getLines.map(_.toDouble))
      b.append(f(i)+"\n")

    print(b.result)
  }
}