import kotlin.math.*

fun g(n: Long): Long = floor(sqrt(n.toDouble())).toLong()

fun f(m: Long, n: Long): Long {
    for (i in 3..m) if (n%i==0L) return i
    return if (n!=4L&&n%2==0L) n/2 else n
}

fun main(args: Array<String>) {
    val n = readLine()!!.toLong()
    println(f(g(n),n))
}