import math._

object Main {
  def calc(n: Long): Long = {
    if (n % 3 == 0) return 3
    if (n % 4 == 0) return 4

    var x = n
    while (x % 2 == 0)
      x /= 2

    var p = 3L
    while (p * p <= x) {
      if (x % p == 0) return p
      p += 2
    }
    x
  }

  def main(args: Array[String]) = {
    val sc = new java.util.Scanner(System.in)
    val n = sc.nextLong

    println(calc(n))
  }
}