import java.util.*;
class A {
	static Scanner s = new Scanner(System.in);

	public static void main(String[] args) {
		long in = s.nextLong();
		if(in%3==0){
			System.out.println(3);
			return;
		}
		if(in%4==0){
			System.out.println(4);
			return;
		}
		long l = (long)(Math.sqrt(in)+0.6);
		long c = 5;
		while(in%c!=0){
			c+=2;
			if(c>l){
				System.out.println(in);
				return;
			}
		}
		System.out.println(c);
	}
}