package codeforces;
import java.util.Scanner;
/**
* Created by sherxon on 2016-12-25.
*/
public class BachgoldProblem {
public static void main(String[] args) {
Scanner in=new Scanner(System.in);
int n=in.nextInt();
if(n%2==0){
System.out.println(n/2);
for (int i = 0; i <n/2 ; i++) {
System.out.print(2 + " ");
}
}else{
System.out.println((n-3)/2+1);
for (int i = 0; i <(n-3)/2 ; i++) {
System.out.print(2+" ");
}
System.out.print(3);
}
}
}