package main

import "fmt"

func main() {
	var n int64
	fmt.Scan(&n)
	ans := n
	if n%2 == 0 {
		ans = n / 2
	}
	for i := int64(3); i*i <= n; i++ {
		if n%i == 0 {
			ans = i
			break
		}
	}
	fmt.Println(ans)
}