import java.util.*;

public class Main {
  public static void main(String[] args) {
    Scanner sc = new Scanner(System.in);
    long n = sc.nextLong();
    long ans = 1;
    for(long i = 3; (i * i) <= n; i++) {
      if((n % i) == 0) {
        ans = i;
        break;
      }
    }
    if(ans == 1) ans = n;
    System.out.println(ans);
  }
}