import java.util.Scanner; public class Main { public static void main(String[] args){ Scanner in = new Scanner(System.in); while(in.hasNext()){ solution(in); } } /** * 数学法 * @param in */ private static void solution(Scanner in){ int n = in.nextInt(); int count = 0; for(int num=2,remain=n-num; num<=remain; num++,remain--){ // 素数对 if(isPrime(num) && isPrime(remain)){ count++; } } System.out.println(count); } /** * 是否素数 * @param num * @return */ private static boolean isPrime(int num){ if(num <= 1){ return false; } if(num == 2){ return true; } for(int i=2; i<=Math.sqrt(num); i++){ if(num%i == 0){ return false; } } return true; } }