import scala.annotation.tailrec
import scala.io.StdIn

object Problem312 {

  def primeFactorization(n: Long): Seq[Long] = {
    @tailrec
    def factor(n: Long, div: Long, result: Seq[Long]): Seq[Long] = {
      if (n < div * div) {
        n +: result
      } else if (n % div == 0) {
        factor(n / div, div, div +: result)
      } else {
        factor(n, div + 1, result)
      }
    }
    factor(n, 2, Nil)
  }

  def proc(n: Long): Long = {
    val pf = primeFactorization(n)

    val minPrime = pf.filter(_ != 2).reduceOption(_ min _).getOrElse(n)
    val minComposite = pf.sorted.take(2).product

    minPrime min minComposite
  }

  def main(args: Array[String]) {
    val n = StdIn.readLong()
    val result: Long = proc(n)
    println(result)
  }
}