import java.util.*;

public class Main {
  public static void main(String[] args) {
    Scanner sc = new Scanner(System.in);
    long n = sc.nextLong();
    long ans = (long)Math.pow(10, 18);
    for(long i = 2; (i * i) <= n; i++) {
      if((n % i) == 0) {
        if(i == 2) {
          ans = Math.min(n / 2, ans);
        } else {
          ans = Math.min(ans, i);
        }
      }
    }
    if(ans == Math.pow(10, 18)) ans = n;
    System.out.println(ans);
  }
}