import java.util.Scanner;

public class Main {
	public static void main(String[] args) {
		Scanner scan = new Scanner(System.in);
		long N = scan.nextLong();
		int M = (int)Math.sqrt(N);
		boolean primeList[] = new boolean[M+1];
		for(int i=2; i<=M; i++) {
			primeList[i] = true;
		}
		
		for(int i=2; i<=M; i++) {
			if(primeList[i]) {
				for(int j=i+i; j<=M; j=j+i) {
					primeList[j] = false;
				}
			}
		}
		
		for(int i=3; i<=M; i++) {
			if(primeList[i]) {
				if(N%i == 0) {
					System.out.println(i);
					break;
				}
			}
		}
	}
}