import scala.io.StdIn._


object Main {
  def main(args: Array[String]): Unit = {
    val n = readLine.toInt
    println(f"${solve(n)}")
  }


  def solve(n: Int): Long = {
    def lowerbound(ub: Long, lb: Long, f: (Long) => Boolean): Long = {
      if(ub-lb <= 1) return lb*lb
      val m = (ub+lb)/2
      if(f(m)) lowerbound(m,lb,f)
      else lowerbound(ub,m,f)
    }

    lowerbound(n.toLong,0,(x:Long) => x*x > n.toLong)
  }
}

