2098

import java.util.Scanner;

public class Main{
public static boolean Prime( int a){
    if (a == 2)
        return true;
    for (int i = 2; i <=Math.sqrt(a); i++) {
        if(a%i == 0 )
            return false;
    }
    return true;
}
    public static void main(String[] args) {
         Scanner sc = new Scanner(System.in);
         while (sc.hasNext()){
             int x=sc.nextInt();
             if (x==0) break;
             int i,c = 0;
             for (i = 2; i < x-i ; i++) {
                 if(Prime(i)&&Prime(x-i))
                     c++;
             }
             System.out.println(c);
         }
    }
}