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= {
    var ans = 0
    while(ans * ans <= n){
      ans += 1
    }
    (ans-1) * (ans-1)
  }
}
